Matthew Poole and continuators on Numbers 24:3

3 And he took up his parable, and said, Balaam the son of Beor hath said, and the man whose eyes are open , hath said;

The eyes, either 1. of his body, as in the following verse: or 2. of his mind, which God had opened in a peculiar and Prophetical manner, whence Prophets are called Seers, 1 Sam. 9. 9. He implies that before he was blind and stupid, having eyes, but not seeing nor understanding Some render the words, having his eyes shut, as the Hebrew verb Satham signifies, the letters Schin and Samech being frequently exchanged, and so the meaning is, that he received this revelation either in a dream, when mens eyes are simply shut; or in an extasie or trance, when mens eyes, though open, are in a manner shut, to wit, as to the use and exercise of them.

Marginal references: chap. 23. 7, 18.; Heb. who had his eyes shut, but now open.