(one's) handshake is (one's) word
When one promises or agrees to something and shakes another person's hand, one is morally obliged to upholding that pledge. A: "So, $500, like we agreed?" B: "Of course, my handshake is my word." Hey, you can't back out now. We shook on it, and your handshake is your word! Tom's handshake is his word, so if he said he'd be over first thing in the morning to sign the papers, he will be.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.