With the word “for,” Peter sets out to demonstrate that his instruction in the previous two verses did not come from his own thinking but is simply the instruction of God as revealed and confessed in the Old Testament. As he had done earlier (in 1 Peter 2:3) Peter draws his readers’ attention to Psalm 34:1–22.
10 For “Whoever desires to love life and see good days, let him keep his tongue from evil and his lips from speaking deceit;