Psalms 71:15

My mouth shall show forth thy righteousness
Both his punitive justice in taking vengeance on his enemies, agreeably to the above imprecations; and his faithfulness in the performance of promises of good things unto him; as also his essential righteousness displayed and glorified in the redemption that is by Christ; and particularly the righteousness of Christ, accepted of God, and imputed by him; which the psalmist with his mouth declared his faith in, expressed his joy at, and set forth in a strong manner the glory and excellency of it, and determined to make mention of it, and of that only, as in ( Psalms 71:16 ) ;

[and] thy salvation all the day;
both temporal and eternal; the glory of both, and praise for the same;

for I know not the numbers [thereof];
of that righteousness and salvation, the numerous blessings which are contained in them; see ( Psalms 40:5 ) ; or "though I know not the numbers of them" ^F3; though he could not fully declare the glories and excellencies of the righteousness and salvation of God, and the numerous mercies and rich grace included in them; yet he would attempt to set them forth in the best way he could, though in a feeble and imperfect manner.