God is the refiner of His people, as the precious metals have to be separated from the dross that clings to them. Proverbs 25:4 (where the A.V. has ' finer '); Isaiah 48:10; Zechariah 13:9; Malachi 3:2,3 . So God tests the believer's heart (1 Thessalonians 2:4 ), and his faith, which leads to endurance. James 1:12; 1 Peter 1:7 .