15:13 Thou in thy mercy hast led forth the people which thou hast redeemed: thou hast guided them in thy strength unto thy holy habitation.
15:25 And he cried unto the LORD; and the LORD shewed him a tree, which when he had cast into the waters, the waters were made sweet: there he made for them a statute and an ordinance, and there he proved them,
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 .