O Jehovah,! thy tender mercies are many; as if he had said that no offenders are safe but those who betake themselves to the divine mercy. Farther, to encourage himself to approach God with the greater confidence, he not only says that God is merciful, but he mightily magnifies and extols his compassion's. From this we gather that he was so contented with them, as not to seek any aid from his own merits. It is however at the same time to be noted, that the Prophet was far from being lightly troubled with many temptations, seeing he was forced to oppose to them this vast abundance of mercy. It makes little difference whether we read great or many The prayer which follows, Quicken me according to thy judgments, I explain as referring to the promises. The original word for judgment is by some translated manner or custom; but I have already shown above that such a translation is less suitable than the other. The Prophet then again confirms the truth, That life cannot be hoped for or asked from God, unless hope is produced by his word; and he often repeats this truth, because it is one of which we are marvelously forgetful. But that we may boldly appropriate to ourselves all the grace which God promises to his servants, let the doctrine of the great and manifold tender mercies of God be ever present to our thoughts. If we imagine that God makes his promises because he is bound to do it, or because we have deserved it, doubting or mistrust will steal upon our minds, which will shut the gate against our prayers. But if we are thoroughly persuaded that the sole cause by which God is moved to promise us salvation is the mercy inherent in his own nature, we will approach him without hesitation or doubt, because he has bound himself to us of his own accord.

Great are thy tender mercies, O Lord - They are many, or multiplied. The word rendered "tender mercies" is the same which occurs in Psalm 40:11; Psalm 51:1; Psalm 69:16; Psalm 79:8; Psalm 103:4. See the notes at Psalm 25:6.
Quicken me - See Psalm 119:149.

Great are thy tender mercies - They are רבים rabbim, multitudes. They extend to all the wretchednesses of all men.

Great [are] thy tender mercies, O LORD: quicken me according to thy (b) judgments.
(b) According to your promise made in the law, which because the wicked lack they have no hope of salvation.

Great are thy tender mercies, O Lord,.... Not his providential mercies only, which are many and undeserved, and constantly repeated; but his special mercies in Christ, which flow from the tenderness of his heart; and his merciful lovingkindness to his people, and which are great or many (f), as to quantity; there being a multitude of them, not to be reckoned up: and for quality they are wonderful beyond expression and conception; proceed from unmerited love, rich, free, sovereign grace, and last for ever;
quicken me according to that judgments; See Gill on Psalm 119:149.
(f) "multae", Pagninus, Montanus, Musculus, Michaelis.

(See on Psalm 119:149).