Romans 3:3

3:3 What then? If some did not believe, does their unbelief nullify the faithfulness of God?

Romans 11:20

11:20 Granted! They were broken off because of their unbelief, but you stand by faith. Do not be arrogant, but fear!

Romans 11:23

11:23 And even they – if they do not continue in their unbelief – will be grafted in, for God is able to graft them in again.