If Bil'am was a prophet, why did Hashem need to open his eyes to see an angel?
Ramban: This Pasuk is proof that he was not a prophet (who sees angels whenever he prophesies), 1 but a plain sorcerer 2 - who initially received the word of Hashem, 3 and who will shortly merit a 'vision of Shakai' 4
Ramban: See above, Pasuk 8.
Later in 4:16, all in honor of Yisrael. See Ramban, end of Dibur.