Adam Clarke on Jeremiah 17:5

Cursed be the man that trusteth in man - This reprehends their vain confidence in trusting in Egypt, which was too feeble itself to help, and, had it been otherwise, too ill disposed towards them to help them heartily. An arm of flesh is put here for a weak and ineffectual support. And he who, in reference to the salvation of his soul, trusts in an arm of flesh - in himself or others, or in any thing he has done or suffered, will inherit a curse instead of a blessing.