Arthur T. Pierson (1837-1911) followed Charles Spurgeon as pastor of Metropolitan Tabernacle, was a consulting editor for the original Scofield Study Bible, wrote an excellent biography of George Muller, and co-edited The Fundamentals. Here is his description, published in 1894, of the difference between eternal life and eternal rewards:

“With many disciples, the eyes are yet blinded to this mystery of rewards, which is one of the open mysteries of the Word, and some cannot see how rewards can have any place in an economy of grace. But we must not confound salvation and recompense. It must be an imputed righteousness,—exceeding by faith that of the most proper Pharisee—whereby we enter the Kingdom of Heaven; but, having thus entered by faith, our works determine our relative rank, place, and reward, in that kingdom. Eternal life is God’s gift to be had for the asking; but he who receives the gift, and does work, sowing and reaping for God, receiveth also wages and gathereth fruit unto life eternal” (Pierson, The New Acts of the Apostles, p. 417, quoted in David E. Seip, A Victorian Dissenter, p. 156).