John Trapp on Proverbs 3:5

Verſ. 5. Truſt in the Lord] To truſt in God is to bee unbottomed of thy ſelf, and of every creature, and ſo to lean upon God, that if hee fail thee thou ſinkeſt. Confidence is the leaſt, and yet the beſt wee can render to the Lord, for hereby wee acknowledge his Soveraignty, and ſet the Crown upon his head, as it were. See Judg. 9.15.

And lean not to thine own underſtanding] Which becauſe men do, hence it is many times, that the faireſt bloſſoms of their endeavours wither, and the unprobableſt things do come to paſs: God loves to confute men in their confidences, as hee did the Philiſtims in their Champion Goliah. Wee muſt not therefore truſt, no not Truſt it ſelf, but God on whom it relies, who is therefore called our Truſt. They truſt not God at all, that do it not alone. He that ſtands with one foot on a rock, and another foot upon a quickſand, will ſink and periſh as certainly, as he that ſtands with both feet on a quickſand. Lord lead mee to a Rock that is higher than I, ſaith David. Whither when hee was once got, then hee ſate and ſang, The Lord is my rock and my ſalvation, &c. Pſal. 27.1. Surely as one ſaid of general Councils, they ſeldome were ſucceſſeful, becauſe men came with confidence, leaning to their own underſtanding, and ſeeking for victory, rather than verity: ſo it holds as true in other like caſes.