The Quran Verse
Surah 12:13:
[Jacob] said, 'Indeed, it saddens me that you should take him, and I fear that a wolf would eat him while you are of him heedless.'
In Genesis, it is the brothers who invent the idea of a "wild animal" after the fact to hide their crime. In the Quran, Jacob gives them the idea by mentioning a wolf beforehand.
This is a narrative "pre-echo" common in folk literature. By having Jacob suggest the wolf, the Quranic author creates a more poetic, irony-filled story, but one that diverges from the psychological realism of the original biblical text.