Confirm thy word unto thy servant. Here we have briefly set forth the sole end and legitimate use of prayer, which is, that we may reap the fruits of God's promises. Whence it comes to pass, that they commit sin who utter vague and incoherent desires. For we perceive the prophet allows not himself to petition or wish any thing but what God hath condescended to promise. And certainly their presumption is great, who rush into the presence of God without any call from his word; as if they would make him subservient to their humor and caprice. The argument by which the Psalmist enforces his plea deserves to be noticed; because I am devoted to thy fear. The relative 'sr asher, in this place bears the signification of the causal conjunction, because or for. The prophet intimates that he does not content himself with mere temporal enjoyments, as worldly men do; and that he did not make a preposterous abuse of God's promises, to secure the delights of the flesh, but that he made his fear and reverence his aim. And truly the best assurance which we can have of obtaining our requests is when these and God's service harmonize, and our sole desire is that he may reign in and over us.

Stablish thy word unto thy servant - Confirm it; make it seem firm and true; let not my mind be vacillating or skeptical in regard to thy truth. This seems to be a prayer against the influence of doubt and scepticism; a prayer that doubts might not be suffered to spring up in his mind, and that the objections and difficulties of scepticism might have no place there. There is a class of people whose minds are naturally skeptical and unbelieving, and for such people such a prayer is especially appropriate. For none can it be improper to pray that the word of God may always seem to them to be true; that their minds may never be left to the influence of doubt and unbelief.
Who is devoted to thy fear - literally, "Who," or which, "to thy fear." This may refer either to the author of the psalm, or to the word of God. It may mean that he was among those who feared - that is, worshipped God; or, that the word of God had reference to the "fear," that is, to the worship of God, or was designed to secure that. The construction seems to demand the latter interpretation; and then the prayer is, that God would confirm his faith in that "word" - in that revealed truth - which was designed to secure the worship of God.

Stablish thy word - Fulfil the promises thou hast made to me.

Stablish thy word unto thy servant,.... Either God's word of promise, which never fails, is firm and stable in Christ; and the sense is, that God would assure him of the fulfilment of it, and give him a strong faith and firm belief of it; for otherwise the word of the Lord cannot be surer or more stable than it is: or else the word of his grace; and then the sense is, that he might be established in it, and the truths of it, and be established by it; for the word is a means of establishment, and a good thing it is to have the heart established with grace, with the doctrine of grace, Hebrews 13:9;
who is devoted to thy fear; who served the Lord with reverence and godly fear; who feared the Lord and his goodness; that grace being a reigning one in his heart, and ever before his eyes. Or, "which is unto thy fear" (d); that is, which word is unto thy fear; which leads unto it, and has a tendency to promote and increase it; and so is a commendation of the word of God from this effect of it.
(d) "quod ad timorem tuum", Pagninus, Montanus; "quod ad timorem tui facit", Musculus; "et ducit", Schmidt; "quod datum est ad timorem tui", Michaelis.

who is devoted to thy fear--or better, "which (that is, Thy word) is for Thy fear," for producing it. "Which is to those who fear Thee." God's word of promise belongs peculiarly to such (compare Genesis 18:19; 1-Kings 2:4; 1-Kings 8:25) [HENGSTENBERG].

Stablish - Confirm and perform thy promises.