en_tn/2co/01/22.md

he set his seal on us

Paul speaks of God showing that we belong to him as if God had put a mark on us as a sign that we belong to him. Alternate translation: "he has put his mark of ownership on us" or "he has shown that we belong to him" (See: rc://en/ta/man/translate/figs-metaphor)

gave us the Spirit in our hearts

The word "heart" is often used to refer to the innermost part of a person. Alternate translation: "gave us the Spirit to live within each of us" (See: rc://en/ta/man/translate/figs-metonymy)

the Spirit ... as a guarantee

The Spirit is spoken of as if he were a partial downpayment toward eternal life. (See: rc://en/ta/man/translate/figs-metaphor)