What they did was "out of envy"...
What they did was "out of envy", "that Allâh should send down of His grace on whomsoever of His servants He pleases" was the object of their envy. "so they returned with wrath upon wrath", that is, they returned doubly enraged. It may also mean that they invited double wrath of Allâh upon themselves - the first because they disbelieved in Torah and the second because they disbelieved in the Qur’ân.
The verse says that they were partisans of the Prophet long before he was born; they prayed to Allâh for victory by his name and his Book. When the Prophet was sent and the Qur’ân was revealed, they very well recognized that he was the Prophet in whose name they used to pray for victory, and whose coming they awaited. But they were overwhelmed by envy and arrogance.
No sooner did the Prophet begin his call then they denied his truth, and forgot all that they used to tell about the awaited prophet. It was not surprising as they had earlier disbelieved in Torah too. Thus they committed disbelief after disbelief, and invited the wrath of Allâh upon themselves, not once but twice. QUR’?N: and they deny what is besides that: That is, they claim that they do not believe in any book other than Torah; but the fact is that they do not believe even in Torah.
QUR’?N: Say: "Why then did you kill Allâh's prophets. . . ": The conjunctive, "then", serves to relate this question to their claim, "We believe in that which was revealed to us". If this claim of yours is correct then why did you kill the prophets of Allâh? And why did you disbelieve in Musâ by taking the calf for a god? And why did you say, "We hear and disobey", when We took a promise from you and lifted the mountain over you?
QUR’?N : and they were made to imbibe (the love of) the calf into their hearts: "al-Ishrâb" ( = to make to imbibe, to make to drink). Instead of saying `the love of the calf', the verse says, "to imbibe the calf", for emphasis, as though they had drunk the calf itself into their hearts. The sentence thus contains two metaphors - "the calf" for the love of the calf, and imbibing into hearts for loving. QUR’?N : Say: "Evil is that which your belief bids you. . .
": It is a derisive expression ridiculing them for their killings of the prophets, their disbelief in Musâ and their arrogance in committing sin after sin and then claiming that they were the true believers. The verse tauntingly asks them: Is this what your belief bids you?