Geneva Bible Notes Reformed @genevanotes

The king's heart [is] in the hand of the LORD, [as] the rivers of water: he turneth it wherever he will. (a) Though kings seem to have all things at commandment, they are not able to bring their own purposes to pass unless God has appointed: much less are the inferiors able.

Keil & Delitzsch Lutheran @keilanddelitzsch

Pro 21:1 The group, like the preceding one, now closes with a proverb of the king. A king's heart in Jahve's hand is like brooks of water; He turneth it whithersoever He will. Brook and canal (the Quinta: ὑδραγωγοί) are both called פּלג, or פּלג, Job 20:17, Arab. falaj (from פּלג, to divide, according to which Aquila, Symmachus, and Theodotion, διαρέσεις; Venet.