Romans 4:20

4:20 He did not waver in unbelief about the promise of God but was strengthened in faith, giving glory to 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.