when he had cast into the waters
These bitter waters were in the very path of the Lord's leading, and stand for the trials of God's people, which are educatory and not punitive. The "tree" is the cross (Galatians 3:13) which became sweet to Christ as the expression of the Father's will (John 18:11). When our Marahs are so taken we cast the "tree" into the waters. (Romans 5:3); (Romans 5:4).