New Defender's Study Bible Notes
40:6 mine ears. The “opened ear” refers to the boring of a hole in the ear of a bond servant who, after becoming eligible for freedom, chooses instead to remain forever in the service of his master (see Exodus 21:6). This ritual symbolized the dedication of the servant to hear and obey only his master’s orders.
40:7 Lo, I come. That this psalm is a Messianic psalm is certain because of its application in Hebrews 10:5-10. It is prophetic of the thoughts in the heart of Christ, possibly as He hung on the cross, remembering how and why He had come into the world.
40:8 to do thy will. Just as the servant with the “opened ear,” Christ had come solely to do the will of the One who sent Him. It is significant that in quoting the psalm the author of Hebrews translated “mine ears hast thou opened” by “a body hast thou prepared me” (Hebrews 10:5). Not just the ear, but the whole body was to be made an offering for sins forever (Hebrews 10:10-12).