51وَإِذْ وَٰعَدْنَا مُوسَىٰٓ أَرْبَعِينَ لَيْلَةً ثُمَّ ٱتَّخَذْتُمُ ٱلْعِجْلَ مِنۢ بَعْدِهِۦ وَأَنتُمْ ظَـٰلِمُونَ
52ثُمَّ عَفَوْنَا عَنكُم مِّنۢ بَعْدِ ذَٰلِكَ لَعَلَّكُمْ تَشْكُرُونَ
[51-52] Call to mind that when We invited Moses for a fixed term of forty nights and days,67 you took to calf worship in his absence.68 Though you had committed a wicked transgression, yet We pardoned you even after that so that you might become grateful.
67When after their escape from Egypt the Israelites entered the Sinai Peninsula, Allah invited the Prophet Moses to Mount Tur for forty days and forty nights to give him Laws, Instructions and Commands for the guidance of the people who had recently been liberated from slavery. (For details, please see Exodus, chaps. 24 to 31). It should, however, be noted that the Tur, referred to here, is not the modern port of Tur on the eastern shore of the Gulf of Suez.
68Cow-worship was very common in Can'an, Egypt and the neighbouring countries. When the Israelites degenerated and became slaves of the Copts after the death of the Prophet Joseph, they learnt this evil practice too from their rulers along with other evils. (The incident of the calf-worship is given in detail in Exodus, 32).