What does Genesis 17:22 mean?

God's relatively lengthy encounter with Abraham ends here. For the first time, we're told about God's departure from one of these meetings. He "went up" from Abraham. Perhaps this detail is included to emphasize that God's appearance to Abraham really happened. It wasn't something Abraham imagined. God came. God spoke. God left. The words here suggest the idea of Abraham being left with a choice: will he believe, trust, and obey? Again on his own, Abraham must believe and act on what God had said. He does so in the following verses.

This willingness to follow God's instructions, and to do so immediately, is a key aspect of Abraham's character. This is the attitude which leads to Abraham being a model of godly faith: trusting obedience in the face of doubt (Romans 4:3). That compliance will be severely tested later on, when God gives an unimaginably difficult to command to Abraham (Genesis 22:2). The end result of that event is one of the Bible's greatest examples of faith (Hebrews 11:17–19).