His last command
In deep conviction we join Robert E. Speer who writes in Missionary Principles and Practice,
The last command of Christ is often set forth as alike the primary and conclusive argument for missions. What was the last command of His lips must have been one of the dearest desires of His heart.
But the work of missions is our duty, not chiefly because of the desire of His heart. He bade His Church to evangelize the world because He wanted it evangelized, and He wanted it evangelized because He knew that it needed to be evangelized. Our duty in the matter is determined not primarily by His command, but by the facts and conditions of life which underlie it.
Even if Jesus had not embodied the missionary duty of the Church in the “great commission,” we should be under obligation to evangelize the world by reason of the essential character of Christianity and its mission to the world
George W. Peters, A Biblical Theology of Missions (Chicago, IL: Moody Press, 1972), 347.