He is known as the "father of faith missions". Started one of the first missions to the Muslims. He believed the churches should be given over to indigenous peoples as soon as possible, so that they don't have to rely on outsiders to run their churches, or do their training. Indigenous believers should be responsible for their own churches and methods of finance, training and authority. He declared, “My earnest desire is to re-model the whole plan of missionary operations so as to bring them to the simple standard of God’s word."
While engaged in dental practice, Groves became convinced from his reading of the New Testament that Jesus intended his disciples in every age to take literally the instructions given in the Sermon on the Mount. The result was a small booklet published in 1825 with the title Christian Devotedness, in which he encouraged his fellow believers to give away their savings and possessions, and assist in proclaiming the Gospel throughout the world. (source)
Groves called upon other missionaries to live lives of simplicity and to trust that God would supply what they needed, he called them to live by faith. Many were unhappy with him over this, but some listened. One named, John Aroolappen, lived as a missionary by faith and successful ministry in South India, leading to a mini-revival and several new churches being formed.
Groves was less of a church builder and more of a steady evangelist and teacher. His focus was on helping people understand God.
He left behind a legacy to emulate on trusting God and being devoted to one's calling.