From Charles Spurgeon's The Treasury of David, additional notes on Psalm 111:
Verse 1. With my whole heart. We see the stress here laid upon a whole heart, and the want of which is the great canker of all vital godliness. Men are ever attempting to unite what the word of God has declared to be incapable of union—the love of the world and of God—to give half their heart to the world, and the other half to God. Just see the energy, the entireness of every thought and feeling and effort which a man throws into a work in which he is deeply interested; the very phrase we use to describe such an one is, that "he gives his whole mind to it." Attempt to persuade him to divert his energies and divide his time with some other pursuit, and he would wonder at the folly and the ignorance that could suggest such a method of success. "Just take a hint from Satan, "says some one; "see how he plies his powers on the individual, as if there were but that one, and as if he had nothing else to do but to ruin that one soul." It was a holy resolution of the Psalmist that he would praise God; and a wise one to add, "with thy whole heart."And we have the result of this determination in the following verses of the psalm.—Barton Bouchier.