Verse 15. This mercy to the aged proves the faithfulness of their God, and leads them to shew that the Lord is upright, by their cheerful testimony to his ceaseless goodness. We do not serve a Master who will run back from his promise. Whoever else may defraud us, he never will. Every aged Christian is a letter of commendation to the immutable fidelity of Jehovah.
He is my rock, and there is no unrighteousness in him. Here is the psalmist's own seal and sign manual; still was he building upon his God, and still was the Lord a firm foundation for his trust. For shelter, for defence, for indwelling, for foundation, God is our rock; hitherto he has been to us all that he said he would be, and we may be doubly sure that he will abide the same even unto the end. He has tried us, but he has never allowed us to be tempted above what we are able to bear: he has delayed our reward, but he has never been unrighteous to forget our work of faith and labour of love. He is a friend without fault, a helper without fail. Whatever he may do with us, he is always in the right; his dispensations have no flaw in them, no, not the most minute. He is true and righteous altogether, and so we weave the end of the psalm with its beginning, and make a coronet of it, for the head of our Beloved.
It is a good thing to sing praises unto the Lord, for "he is my rock, and there is no unrighteousness in him."
EXPLANATORY NOTES AND QUAINT SAYINGS
Verse 15. He is my rock, and there is no unrighteousness in, him. Implying that God can no more be moved or removed from doing righteously, than a rock can be removed out of its place. --Joseph Caryl.
HINTS FOR PASTORS AND LAYPERSONS
Verse 15-16. The reason and the pledge of final perseverance. --C.A. Davis.