1 Corinthians 4:17

4:17 For this reason, I have sent Timothy to you, who is my dear and faithful son in the Lord. He will remind you of my ways in Christ, as I teach them everywhere in every church.

1 Corinthians 15:2

15:2 and by which you are being saved, if you hold firmly to the message I preached to you – unless you believed in vain.