It was the practice of these idolaters to revere whatever customs they found their forefathers doing. In fact it was the most important rule of their society and whoever hesitated to accept something or rejected part of their culture he was considered to have dishonored the ancestors by not giving them their proper respect. This was considered to be disobedience as well as being injurious to keeping alive their memory. As a result the biggest obstacle to the message of tawheed that all of the prophets and messengers came with was ancestor worship in the form of blindly and unquestioningly following their customs and practices.
The people of Musa rejected the message of tawheed because they felt unable to turn away from the practices of their forefathers and become followers of something new. Allah the Most High says:
They said: "Have you come to us to turn us away from that (Faith) we found our fathers following, and that you two (i.e. Musa and Harun may have greatness in the land? We are not going to believe you two!" [Surah Yunus : verse 78]
And Ibraheem addressed his people saying:
"What do you worship?" They said: "We worship idols and to them we are ever devoted." He said: "Do they hear you when you call on (them)? Or do they benefit you or do they harm (you)?" They said: "(Nay) but we found our fathers doing so." [Surah Ash-Shu'araa: Verse 70-74]
When Ibraheem presented such a strong and silencing argument that made clear the foolishness of idol worship and made clear that what they were following didn't stand up to reason or revelation, they turned to the only explanation they had left which was blind and unquestioning adherence to the cultural heritage they had inherited from their forefathers.
Then Prophet Ibraheem made it clear that Islam does not give any weight to customs and habits inherited from ancestors if they conflict with divinely revealed truth. Allah the Most High says:
"He (Ibraheem) said: "Do you observe that which you have been worshipping - you and your ancient fathers? Verily they are enemies to me, save the Lord of the Alamin (mankind, jinn and all that exists)" [Surah Ash-Su'araa : Verse 75-77]
In this verse Ibraheem openly declares that he has disassociated himself from their false and invented gods and he announces his enmity towards them and their deviant ways. We find that Allah mentions this again in another place in the Qur'an:
He (Ibraheem) said: "Indeed you and your fathers have been in manifest error." [Surah Al-Anbiya : Verse 54]
Allah also says:
"Indeed there has been an excellent example for you in Ibraheem (Abraham) and those with him, when they said to there people: "Verily we are free from you and whatever you worship besides Allah: we have rejected you, and there has started between us and you hostility and hatred forever until you believe in Allah Alone" [Surah Mumtahanah : Verse 4]
This method of shunning and disassociation from those who have deviated from the right path and refusing to engage in pointless argumentation is taken from the minhaj (methodology, way) of the messengers of Allah. And it is not something that was intended to be applied only to certain people rather it is to be applied to all who associate partners with Allah in their worship and oppose the true religion of Allah- in every era.
And likewise the pre-Islamic Arabs, when they were called to the Book that Allah had revealed and to the truth that the Prophet Muhammad came with, they were stubborn and obstinate in their refusal and said:
"Enough for us is that which we found our fathers following"! [Surah Al-Ma'idah : Verse 104]
They also said:
"Nay! We shall follow what we found our fathers following." [Qur'an 2:170]
They only resorted to this argument because they had no other excuse. Their argument was not credible nor was it based upon sound reasoning nor did they have proof from any book and it is for this reason that Allah said about them:
"Yet of mankind is he who disputes about Allah without knowledge or guidance or a book giving light! And when it is said to them: "Follow that which Allah sent down", they say: "Nay, we shall follow that which we found our fathers following." [Surah Luqman : Verse 20-21]
And in general this was how every nation of people rejected the prophets and messengers sent to them by Allah even though the message they were sent with was full of light and guidance. Allah documented in His Book what the unbelieving Arabs said as well as what all unbelievers say with His statement:
"Or have we given them any Book before this (the Qur'an) to which they are holding fast? Nay! They say: "We found our fathers following a certain way and religion, and we guide ourselves by their footsteps." And similarly, We sent not a warner before you (O Muhammad) to any town (people) but the luxurious ones among them said: "We found our fathers following a certain way and religion, and we will indeed follow their footsteps." (The warner) said: "Even if I bring you better guidance than that which you found your fathers following?" They said: "Verily, we disbelieve in that with which you have been sent." [Qur'an : Az-Zukhruf : Verse 21-24]
The idolaters fell into blind and unquestioning adherence to the ways of their forefathers so much so that it belittled their intelligence and reduced them to the point that the devil exploited the natural inclination that all human beings have to be loyal to their fathers and grandfathers and the heritage and history that they have inherited from them. This is one of the most dangerous and effective tricks of Satan: he approaches mankind through his desires and love of homeland and love of wealth etc.
In a hasan hadith narrated upon the authority of Sabrah ibn Abee Faakih who said, " I heard the Messenger of Allah say:
"Verily Shaitaan sits on the pathways waiting for the children of Adam. He sits waiting on the pathway to Islam and he says: 'Are you going to accept Islam and leave the religion of your fathers and your fathers' fathers?' When (the son of Adam) disobeys (the Shaitaan) and becomes a Muslim, he then sits waiting on the pathway to hijra and he says: 'Are you going to make hijra and leave your homeland and your status amongst the people? The muhajir is like a man trapped in a strange land, unable to move around except in his own house, and unable to mingle socially except with those few people he has become aquainted with. So his likeness is that of a horse fettered to a post, unable to move around and graze except within the confines of the length of rope, in contrast to the indigenous people of the land who are unconfined and free to move around as they wish.' When (the son of Adam) disobeys (the Shaitaan) and performs hijra, he then sits waiting on the path to jihad and he says: 'Are you going to fight in the way of Allah? It is a hardship on you and your wealth. You will fight and be killed, then someone else will marry your woman and all of your wealth will be divided amongst your inheritors.' However (the son of Adam) disobeys (the Shaitaan) and fights in the way of Allah. Then the Messenger of Allah said: 'Whoever did that then Allah, the Mighty and the Majestic will cause him to enter into Paradise. And whoever was killed then Allah, the Mighty and the Majestic will cause him to enter into Paradise. And if he drowns then Allah will cause him to enter into Paradise. And if his neck was broken by his riding animal then Allah will cause him to enter into Paradise."
Observe that the strategy of Shaitaan that the Prophet has informed us about focuses on the natural inclination that human beings have to protect themselves. The Shaitaan attempts to prevent people from accepting Islam by cautioning them that by doing so they will be going against the customs of their forefathers. And he attempts to prevent Muslims from performing hijra by cautioning them that they will be leaving their homeland and the place where they have status amongst the people. Many poets have expressed the passion with which the idolaters revere their homeland. One such poem reads:
If they had fashioned for me an idol of my homeland
I would have longed to kiss that idol!
If I were unable to dwell in it then I would try to make it dwell within
O my homeland
I hold on to you desperately
As if I met you like a crying youth
I turn my face to you (my homeland) before I turn to the House (Ka'bah) when I take an oath or repent
And the Shaitaan also attempts to prevent Muslims from fighting in the way of Allah cautioning that it is a hardship on the person and his wealth and that he may even be killed. The Shaitaan uses these arguments because he knows that human beings love life and wealth and family.
When the Prophet began calling to the religion of Allah one of the things that the mushrikeen faulted him with was that he called on the people to leave the customs that their fathers and grandfathers closely adhered to. As a result the masses of the people disliked the Prophet and this temporarily hindered the spread of his message.
In a hasan hadith narrated upon the authorityof Urwah ibn Az-Zubair who said: "I asked Abd-Allah ibn 'Amr ibn Al-'Aas: 'What is the worst thing you ever saw the Quraish do to the Messenger of Allah to show their hostility towards him?' He said: 'I was present one day when the most noble members (of the tribe of Quraish) gathered in the Hijr of the Ka'bah and they began to mention the Messenger of Allah. They said: 'We have never had to endure anything like what we have seen from this man. He discredits our intelligence, insults our forefathers, denounces our religion, disassociates himself from us, and insults our gods! We have endured all of these matters of serious consequence.' Or they said something similar to those words.'
(Abd-Allah ibn 'Amr ibn Al-'Aas then) said: 'While they were still talking, the messenger of Allah approached the Ka'bah walking until he reached the Black Stone. As he was making Tawaaf around the Ka'bah he passed by them, and as he was doing so they started to mock him with some of his own statements and the displeasure of the Prophet showed clearly in his face as he passed by. When he passed them a second time they mocked him in a similar fashion and the displeasure of the Prophet showed clearly in his face as he walked by. When he passed by them for the third time they mocked him again so the Prophet said: 'O Quraish! By the One in whose hand is the soul of Muhammad, I have come you with killing!' When they heard the words of the Prophet all of them sat motionless with awe, even those who were the most outspoken against him. Then they began to try to appease the Prophet by being friendly and courteous with him and they said the kindest of words! One of them would said: 'Stop it Abu Al-Qaasim! Go away as one having good faith and upon right guidance! I swear by Allah that you are not stupid!'
(Abd-Allah ibn 'Amr ibn Al-Aas then) said: 'So the Messenger of Allah departed from them. The next day the most noble members of the tribe of Quraish gathered again in the Hijr of the Ka'bah and I was with them. Some of them said to the others: 'Do you remember what happened to you and what he said to you? He said a word to you that you hate and you let him go (without doing anything)!' While they were still talking, the Messenger of Allah approached and they all jumped up and rushed over to him and surrounded him and they said: 'Are you the one who said such and such things about our gods and our religion?' (Abd-Allah ibn 'Amr ibn Al-Aas then) said that the Messenger of Allah said: 'Yes. I am the one who said that.'
(Abd-Allah ibn 'Amr ibn Al-Aas then) said: 'I saw a man from amongst them (Uqba ibn Abi Mu'ait) violently grab the Prophet by his collar. (Abd-Allah ibn 'Amr ibn Al-Aas then) said: 'Abu Bakr began to cry and he stood up behind the Prophet and said: 'Do you want to kill a man just because he says my Lord is Allah?' (Abd-Allah ibn 'Amr ibn Al-Aas then) said: 'That is the worst thing I ever saw the Quraish do to the Prophet."