Charles Ellicott Commentary Numbers 22:33

"and the ass saw me, and turned aside before me these three times: unless she had turned aside from me, surely now I had even slain thee, and saved her alive." — Numbers 22:33 (ASV)

Unless she had turned from me. —There may be an aposiopesis in this verse. Perhaps she turned aside from (or, before) me ... for (otherwise) now I would have killed you, etc. According to this view the angel does not assign a reason why the ass turned aside, but leaves this to be inferred by Balaam. (Compare Keil on this passage.)