en_tn_condensed/rev/14/04.md

they have kept themselves sexually pure

Possible meanings are 1) "they have not had sexual relations with a woman who was not their wife" or 2) "they are virgins."

follow the Lamb wherever he goes

"they do whatever the Lamb does" or "they obey the Lamb"

redeemed from among mankind as firstfruits

"purchased out of the midst of the rest of mankind as a special celebration of salvation"