The Children of Israel worshipped the Calf

Allah then said, "Remember My favor on you when I forgave you for worshipping the calf." This happened after Musa went to the meeting place with his Lord at the end of that period which was forty days. These forty days were mentioned in Surat Al-A`raf, when Allah said,

وَوَعَدْنَا مُوسَى ثَلَـثِينَ لَيْلَةً وَأَتْمَمْنَاهَا بِعَشْرٍ

The Israelites were forgiven only when they had offered Taubah توبہ (repentance), as recounted in Verse 54. In saying that they were pardoned so that they might learn gratefulness, the present verse employs the Arabic word لَعَلَ La` lla which indicates expectation. In the present context it does not mean that Allah had or could have any doubt or misgiving about this or any other matter; what the word implies here is just that when a man receives a pardon, the onlookers may expect him to feel grateful.