The Old Testament describes God's plan as making His enemies His footstool (Ps 110:1). Reigning kings in Old Testament days placed their feet on the prone bodies of their enemies as a sign of bringing them to submission. God's vanquished enemies would likewise be subject to His will (1 Cor 15:27-28).
In the New Testament, God's enemies are described as humbled beneath Jesus' feet (Mt 22:44). Jesus, God Himself, died on His cross for all His enemies (Rm 5:8). He reigns on His cross as crucified King (Jn 19:19).
We all were enemies of Christ the King as we lived in sin (Rm 5:10). Then we came to know Jesus as Savior, Lord, God, and King, and we repented. We came to the foot of His cross and were shocked speechless when we realized how much Jesus, King of the universe, suffered out of love for us (Is 52:15). We humbled ourselves at His crucified feet (Mt 22:44), and we fell at His feet to worship, thank, and praise Him (Lk 17:16).
King Jesus washed our feet; now we "must wash each other's feet" (Jn 13:14). We wash King Jesus' feet by feeding the hungry, welcoming strangers, visiting prisoners, and comforting the ill (Mt 25:35ff).
Have you subjected everything to King Jesus? Give Him your all. Place "all things under His feet" (1 Cor 15:27).