Unfortunately, once you hit send on Facebook Messenger or Chat.. the message will be sent to your friends inbox and will stay there even if you delete the message before they login to their Facebook account. So even if they haven't had a chance to view the message, it will remain in their inbox, even if you delete it on your end.
Below is the message you see in Facebook when you go to delete a message or group of messages you sent... notice the words "delete your copy" below. You can only delete your copy of the messages
Delete These Messages?
Once you delete your copy of these messages, it cannot be undone.