Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Psa 115:1-8) Glory to be ascribed to God.
(Psa 115:9-18) By trusting in him and praising him.
Let no opinion of our own merits have any place in our prayers or in our praises. All the good we do, is done by the power of his grace; and all the good we have, is the gift of his mere mercy, and he must have all the praise. Are we in pursuit of any mercy, and wrestling with God for it, we must take encouragement in prayer from God only. Lord, do so for us; not that we may have the credit and comfort of it, but that they mercy and truth may have the glory of it. The heathen gods are senseless things. They are the works of men's hands: the painter, the carver, the statuary, can put no life into them, therefore no sense. The psalmist hence shows the folly of the worshippers of idols.
It is folly to trust in dead images, but it is wisdom to trust in the living God, for he is a help and a shield to those that trust in him. Wherever there is right fear of God, there may be cheerful faith in him; those who reverence his word, may rely upon it. He is ever found faithful. The greatest need his blessing, and it shall not be denied to the meanest that fear him. God's blessing gives an increase, especially in spiritual blessings. And the Lord is to be praised: his goodness is large, for he has given the earth to the children of men for their use. The souls of the faithful, after they are delivered from the burdens of the flesh, are still praising him; but the dead body cannot praise God: death puts an end to our glorifying him in this world of trial and conflict. Others are dead, and an end is thereby put to their service, therefore we will seek to do the more for God. We will not only do it ourselves, but will engage others to do it; to praise him when we are gone. Lord, thou art the only object for faith and love. Help us to praise thee while living and when dying, that thy name may be the first and last upon our lips: and let the sweet savour of thy name refresh our souls for ever.