By this I know that thou favourest me, because mine enemy doth not triumph over me.

Wesley's Notes

41:11 By this - Because hitherto thou hast supported me, and prolonged my days to the disappointment of their hopes.

Jamieson-Fausset-Brown Bible Commentary

11-13. favourest-or tenderly lovest me (Ge 34:19), evinced by relief from his enemies, and, farther, God recognizes his innocence by upholding him.

Matthew Henry's Concise Commentary

41:5-13 We complain, and justly, of the want of sincerity, and that there is scarcely any true friendship to be found among men; but the former days were no better. One particularly, in whom David had reposed great confidence, took part with his enemies. And let us not think it strange, if we receive evil from those we suppose to be friends. Have not we ourselves thus broken our words toward God? We eat of his bread daily, yet lift up the heel against him. But though we may not take pleasure in the fall of our enemies, we may take pleasure in the making vain their designs. When we can discern the Lord's favour in any mercy, personal or public, that doubles it. If the grace of God did not take constant care of us, we should not be upheld. But let us, while on earth, give heartfelt assent to those praises which the redeemed on earth and in heaven render to their God and Saviour.