وَمَن كَفَرَ فَلا يَحزُنكَ كُفرُهُ ۚ إِلَينا مَرجِعُهُم فَنُنَبِّئُهُم بِما عَمِلوا ۚ إِنَّ اللَّهَ عَليمٌ بِذاتِ الصُّدورِ

Whoever disbelieves, let their disbelief not grieve you [O Muhammad]. To Us will be their return, and We will inform them about what they have done. Indeed, Allah knows best what is in the breasts.

EXPOSITION

Verse 21 described the position of the stubborn disputers regarding God’s call to guidance due to their adherence to blind traditions and customs, which they found their forefathers on. The Quranic discourse in this verse attempts to comfort the Prophet, asking him not to be aggrieved or saddened by the denial and faithlessness of such people^{[1], [2]} (see also 3:176, 5:41, 5:68, 6:33, 10:65, 15:88, 16:127, 18:6, 26:3, 27:70, 35:8, and 36:76).

To Us will be their return, and We will inform them about what they have done. Indeed, Allah knows best what is in the breasts. God shall inform them of their deeds and requite them accordingly.^[3] In this context, Allah knowing best what is in the breasts (3:119, 3:154, 5:7, 8:43, 11:5, 29:10, 35:38, 39:7, 42:24, 57:6, 64:4, 67:13) means God knows what the hearts conceal since nothing is hidden from Him,^[4] including the enmity and antagonism in their hearts.^[5] So therefore, there should be no cause for sadness due to their continued faithlessness.^[6]

[1] Munyah, 21/146.
[2] Tibyan, 8/283; Tabrisi, 8/502.
[3] Tibyan, 8/283; Tabrisi, 8/502.
[4] Tibyan, 8/283; Tabrisi, 8/502.
[5] Munyah, 21/146.
[6] Munyah, 21/146.