L.C.
If someone tells you to bite him back, please disregard.
Get a soft teething ring and put it in the freezer. Also get washrags wet and put them in the freezer. When he starts to bite or even does bite, firmly tell him no and that if he needs to bite he can bite the ring or the washrag. Eventually he will ask for them when he is frustrated.
Provide him with feeling words or other words that he can use. If someone is taking him toy teach him to say, "No" to the child. We even taught a little girl in my class to say, "Unavailable".
Most kids this age bite because they are frustrated. They have no words and few coping skills. It feels powerful and actually provides and immediate release of tension and frustration when they bite down like that. You best bet is giving him other skills and options while correcting the behavior. Help him feel powerful another way and help him relieve tension by giving him something he IS allowed to bite on.
Hope this helps,
L.