[soweak.]

If he is passive, you need to fold here. The 8 is quite an innocuous card as it completes no draws and creates no draws. You may be up against A8o or a made straight or another combination of two pair.

You should decide before the turn comes whether or not you want to go to the showdown with this player. loose/passives will normally call you down even with A-weak because you are the pre-flop raiser. a turn raise in my experience indicates two pair or better in these situations.