The following is an excerpt from The Man & The Story Behind Amazing Grace 
Carey was the third William (Cowper and Wilberforce were the first two), whose life and ministry was greatly affected by John Newton. This former shoemaker became passionate about evangelism after reading the journals of the navigator, James Cook.
Famous for his immortal quote ‘Expect great things from God, Attempt great things for God’, with which he urged a Baptist Association meeting at Nottingham in 1792, this young Baptist cobbler went on to become the founder and father of the modern missions movement.
Carey’s connection with Newton was through the ministry of Thomas Scott and a meeting with William Wilberforce, who were both influenced by Newton.
In 1821 Carey quite openly acknowledged his appreciation for the ministry of Scott: If there be anything of the word of God in my soul, I owe much of it to Scott’s preaching. (Through Many Dangers by B.H.Edwards P. 213)
This is the same Thomas Scott who, following his contact and correspondence with Newton 16 years earlier, had ‘publicly renounced as erroneous and grievous perversion of Scripture’ his liberal thinking on the Trinity and the deity of Christ, and his rejection of the literal teaching of hell and judgment.
Carey was commended to Newton, who in turn introduced him to William Wilberforce who shared his vision for world mission, and sponsored his trip to India.