Striketh hands, in token of his becoming surety; of which phrase, and of the thing itself, see on Proverbs 6:1, Proverbs 11:15. His friend: the friend here is either,
1. Before and to the creditor. Or rather,
2. Before, and with, and for the debtor, for whom, as being his friend, he becomes surety, as the manner of friends is. See on Proverbs 6:3. And this proverb is fitly placed after that, Proverbs 17:17, to intimate, that although the laws of friendship oblige us to love and help our friends in trouble as far as we are able, yet they do not oblige us to become surety for them rashly, and above what we are able to pay, for by that means we make ourselves unable to do good either to them, or to others, or to ourselves.