fautorem] ostendati, [fore amicumi] polliceaturi.
favorer-M-S-ACC show-3-S-SUBJ be-INFIN-FUT friend-M-S-ACC promise-3-S-SUBJ-DEPON
The one who esteems you, [who] shows himself [to be] an admirer of your youthfulness and appearance, should promise he will be your friend.