A friends with benefits question...Please help!!?

Hi. I have a FWB (friends with benefits). I notice that sometimes when we part ways, he says "behave yourself". Does anyone know what the heck this is meant for? I am trying not to read too much into it (as I know how FWB works). But it has been bugging me. Also, sometimes he says "keep your hands in a safe place". What the heck does this guy mean? He says he only has friend feelings towards me. Thanks for the help :)