Turn not away the face of thine anointed - i. e., make him not to hide his face through shame at having his prayers rejected (compare the 1-Kings 2:16 note).
The mercies of David - i. e., "God's mercies toward David."

Turn not away the face of thine anointed - "At least do me good; and if not for my sake, do it for thy own sake." - Jarchi.
These two last verses are not in the parallel place in 1 Kings 8:22-53. There are other differences between the two places in this prayer, but they are not of much consequence.

O LORD God, turn not away the face of (n) thine anointed: remember the mercies of David thy servant.
(n) Hear my prayer, I who am your anointed king.

turn not away the face of thine anointed--that is, of me, who by Thy promise and appointment have been installed as king and ruler of Israel. The words are equivalent in meaning to this: Do not reject my present petitions; do not send me from Thy throne of grace dejected in countenance and disappointed in heart.
remember the mercies of David thy servant--that is, the mercies promised to David, and in consideration of that promise, hear and answer my prayer (compare Psalm 132:10).

Thine anointed - Of me, who by thy command was anointed the king and ruler of thy people: do not deny my requests, nor send me from the throne of thy grace with a dejected countenance. The mercies - Those which thou hast promised to David and to his house for ever. And thus may we plead, with an eye to Christ, who is called David, Hosea 3:5. Lord, remember his merits, and accept of us, on the account of them. Remember the promises of the everlasting covenant, which are called the sure mercies of David, Isaiah 55:3. This must be all our desire, all our hope, all our prayer, and all our plea; for it is all our salvation.