“Jesus, knowing that the Father had given all things into his hands, and that he had come from God and was going back to God, rose from supper” (v3-4). John gives us this short description of Jesus so that we understand: acting like a servant was part of Jesus’ God-nature and his deliberate choice. Washing feet was humbling, an act of loving service (v1) that no king or other human leader would ever do. Yet Jesus did it so that we understand divine love.
“Afterward you will understand” (v7). After the cross, we understand even more: real love, God’s love, means using power not to dominate or destroy, but to serve, rescue, purify, and restore.