And upon your binah do not lean. The perfection of bitachon [is]: that a person trust in Hashem and not trust in another man, and not even in his own strength and the might of his hand, and not in his sechel and his understanding. And it is for this reason that [Shlomo HaMelech] said: “and upon your binah do not lean.”

And because many go astray by trusting in their own binah, [the pasuk] warns concerning this more forcefully than it does concerning trust in wealth or in strength. And a second reason is: that trust in binah includes trust in the others as well; for a person will not come to trust in wealth or in strength, or in anything else, until he sees from his own binah that there is reason to trust in them. It is on this account that he warned, saying: “and upon your binah do not lean.”

And the matter [of what this warning requires] is this: when it appears to you, through your sechel and your understanding, that the deed which you are about to perform will succeed, thanks to the planning of your heart and the plans you have devised, do not trust in this, for everything is dependent upon the hand of Heaven.

This is as it says: “Hashem turns the wise back and renders their knowledge foolish”; and “many are the thoughts in the heart of a man, but the plan of Hashem is what shall stand”; and “if Hashem does not build the house, in vain do its builders labor upon it”; and it is further said: “for all our deeds are vanity”; and it is said: “for the race is not to the swift [and the battle is not to the strong].” And it is said: “to man belong the orderings of the heart, but from Hashem comes the answer of the tongue.” Behold, if even the answer of the tongue is not in the hand of a person, how much more so the deed itself. (Yeshayahu 44:25; Mishlei 19:21; Tehillim 127:1; Yirmiyahu 10:15; Koheles 9:11; Mishlei 16:1)