John Gill Commentary Isaiah 42:20

"Thou seest many things, but thou observest not; his ears are open, but he heareth not." — Isaiah 42:20 (ASV)

Seeing many things, but you observe not The Scribes and Pharisees, saw Christ in the flesh; they saw the miracles he did; they saw the blind receive their sight, the lame walk, the lepers cleansed, the deaf hear, and the dead raised; yet they did not give note to these things, and keep them in their minds, and regard them as clear proofs of his being the Messiah:

opening the ears, but he hears not; they heard John Baptist preach, the forerunner of Christ, and the testimony he bore of him; they heard Christ himself and his apostles; they sometimes opened their ears, and seemed to listen and hear with attention, and wonder at what they heard; and some would own, that never man spoke like Jesus; and yet understood not his speech, and hardened their hearts against him; they saw many things with their bodily eyes, but perceived them not with the eyes of their understandings; they heard with their ears, but understood not in their hearts; for their eyes were shut and their ears heavy, (Isaiah 6:9) (Matthew 13:14Matthew 13:15) .