Jesus answered and said to them, "This is the work of God, that you believe in Him whom He sent."
John 6:29
Surrounding context
6:28 Then they said to Him, "What shall we do, that we may work the works of God?"
6:29 Jesus answered and said to them, "This is the work of God, that you believe in Him whom He sent."
6:30 Therefore they said to Him, "What sign will You perform then, that we may see it and believe You? What work will You do?