John Calvin Commentary Psalms 119:156

"Great are thy tender mercies, O Jehovah: Quicken me according to thine ordinances." — Psalms 119:156 (ASV)

O Jehovah, your tender mercies are many; as if he had said that no offenders are safe except those who turn to the divine mercy. Furthermore, to encourage himself to approach God with greater confidence, he not only says that God is merciful, but he greatly magnifies and praises His compassion.

From this we gather that he was so satisfied with them that he did not seek any aid from his own merits. However, it should also be noted that the Prophet was by no means lightly troubled by many temptations, since he was forced to set this vast abundance of mercy against them.

It makes little difference whether we read great or many. The prayer that follows, Quicken me according to your judgments, I explain as referring to the promises. The original word for judgment is translated by some as 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 remarkably forgetful. But so 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 always be present in our thoughts.

If we imagine that God makes His promises because He is obligated to do so, or because we have deserved them, doubt or mistrust will creep into 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.