Albert Barnes Commentary Psalms 27:9

"Hide not thy face from me; Put not thy servant away in anger: Thou hast been my help; Cast me not off, neither forsake me, O God of my salvation." — Psalms 27:9 (ASV)

Hide not your face far from me — Compare the notes at (Psalms 4:6). To “hide the face” is to turn it away with displeasure, as if we would not look on one who has offended us. The favor of God is often expressed by “lifting the light of His countenance” upon anyone — looking with pleasure or “pleasedly” upon him. The reverse of this is expressed by hiding the face, or by turning it away. The word “far,” introduced by the translators, does not contribute to the meaning of the passage.

Put not your servant away in anger — Do not reject me, or put me away in displeasure. We turn one away, or do not admit him into our presence, with whom we are displeased. The psalmist prayed that he might have free access to God as a Friend.

You have been my help — In days that are past. This he urges as a reason why God should still befriend him. The fact that He had shown mercy to him, and treated him as a friend, is urged as a reason why He should now hear his prayers and show him mercy.

Leave me not — Do not abandon me. This is still a proper ground for pleading with God. We may refer to all His former mercies toward us; we may mention those mercies as a reason why He should now interpose and save us. We may, so to speak, “remind” Him of His former favors and friendship, and may plead with Him that He will complete what He has begun, and that, having once admitted us to His favor, He will never leave or forsake us.