Why will Jesus arise from the Father's right hand?
Jesus will arise from the Father's right hand because His seated position is temporary, bounded by the time word 'until.' When His foes are made His footstool, He will leave heaven, return to this planet, and become King of the promised kingdom.
Les explains that Peter quotes Psalm 110:1, where the Lord says to David's Lord, 'Sit thou on my right hand, until I make thy foes thy footstool.' The word 'until' is a time word, showing that Christ's seated position at the Father's right hand is not forever. David did not ascend into heaven; the Psalm refers to Christ, who was exalted by God's right hand and received the promise of the Holy Spirit, which He shed forth as seen at Pentecost. The manifestation of the Spirit—uneducated Galileans speaking every language, plus other signs and wonders—proved God was in it. Les teaches that one day Christ will arise from that seated position, leave heaven, come back to this planet, and be King of the promised kingdom.
The LORD said unto my Lord, Sit thou at my right hand, until I make thine enemies thy footstool.