2:51
وَإِذْ وَاعَدْنَا مُوسَى أَرْبَعِينَ لَيْلَةً ثُمَّ اتَّخَذْتُمُ الْعِجْلَ مِنْ بَعْدِهِ وَأَنْتُمْ ظَالِمُونَ
2:52
ثُمَّ عَفَوْنَا عَنْكُمْ مِنْ بَعْدِ ذَلِكَ لَعَلَّكُمْ تَشْكُرُونَ
This is the third stage in the divine sociology and the first mention of musa in the whole Quran. musa was ‘promised’ the so-called ’40 nights’ which I read as a period of darkness when musa was raised to a spiritual state (explained in chapter 7). bani israil in the meantime took the calf while they oppressors (possibly to themselves as well).
Allah forgave them after this so they may be grateful (and make full use of the blessings given by him).