Commentary
وَقَالَ الَّذِينَ كَفَرُوا (And those who disbelieve say - 29:12). The infidels had tried all sorts of devices to mislead the Muslims and to hinder the progress of their faith. Sometimes they tried to get hold of Muslims by show of power and wealth, and at others by trying to put doubts in their minds. This verse mentions one such move made by them. They asked Muslims not to leave their ancestral religion in fear of torments in the Hereafter, because no such thing was going to happen at the first place, but even the belief of the Muslims about the Hereafter would come true, they (the infidels) were willing to undertake that they themselves would bear all the torments in the Hereafter on behalf of the Muslims, and the Muslims would not suffer at all.
A similar incident is related in the last ruku' of Surah –Najm أَفَرَأَيْتَ الَّذِي تَوَلَّىٰ وَأَعْطَىٰ قَلِيلًا وَأَكْدَىٰ (Have you seen the one who turned his back, and gave a little, then stopped - 53:33-34). Once some infidels hoodwinked a naive friend of theirs by saying that if he gave them some money here in this world, they would save him in the Hereafter by taking upon themselves his share of the torment. He in fact started paying them the amount, but later stopped it. His foolishness and the absurdity of his action are related in detail in Surah -Najm.
A similar sort of offer made by the infidels to the Muslims is related here. In response to this offer Allah Ta’ ala has said that those who say so are liars. They would not take upon them the burden of any one else. وَمَا هُم بِحَامِلِينَ مِنْ خَطَايَاهُم مِّن شَيْءٍ إِنَّهُمْ لَكَاذِبُونَ (And they are not (able) to bear the burden of their sins in the least. Indeed they are pure liars. -.29:12). It means that when they will see the severity of torment in the Hereafter, they would not dare to take upon themselves the share of anyone else. Hence their promise is false. It is also commented in Surah An-Najm that even if they were ready to take upon them the torment of others, Allah Ta’ ala will not allow it. Because it is against the code of justice that someone else is made to undergo the punishment for the crime committed by another person.
The other point made by the Qur'an here is that although they will not be able to relieve others by taking on themselves the recompense for the sins others have committed, but this much is true that their effort to misguide others and to drift them away from the righteous path is by itself a big sin, which will be loaded upon them in addition to their own sins. This way they will be carrying their own sins as well as that of misguiding others.
Invitation to sin is also a sin, the punishment of which is the same as that of committing it.
It comes out quite clearly from this verse that the one who invites others to sin, or helps others in committing it, is as much a criminal as the one who actually commits it. A hadith quoted by Sayyidna Abu Hurairah ؓ and Anas Ibn Malik ؓ relates that once the Holy Prophet ﷺ said ` Anyone inviting people toward righteousness would be entitled to the collective blessings of all those who would act on his advice, without any reduction from the share of their reward; and anyone inviting people toward sin will also suffer the collective punishment of all those who would act upon his invitation to sin, without any reduction from the punishment of those who have committed that sin'. (Muslim, Ibn Majah, Qurtubi)