The foot as the organ of travel and as a metaphor for life's path. Washing feet was hospitality; putting feet on enemies' necks was victory. God guides the regel of the righteous.
Feet represent direction and allegiance — you go where you place your feet. The Psalms and Proverbs use regel to picture moral choices as paths and the godly life as sure-footed walking.
Isaiah 52:7's beautiful feet of the messenger become Paul's foundation for gospel preaching (Rom 10:15). The foot, as the instrument of going, represents the urgency and beauty of carrying good news.