Seeing many things - That is, the people, the Jews, spoken of here as the servants of God. They had had an opportunity of observing many things pertaining to the law, the government, and the dealing of Yahweh. They had often witnessed his interposition in the days of calamity, and he often rescued them from peril. These things they could not but have observed, much as they had chosen to disregard the lessons which they were calculated to convey.
But thou observest not - Thou dost not keep them (תשׁמר tı̂shmor); thou dost not regard them.
Opening the ears - Thou hast thine ears open. They heard the words of the law, and the instructions conveyed by tradition from their fathers, but they did not lay them to heart, or give heed to them (see the note at Isaiah 6:10).