It is really easy to turn the way of Christ into a series of rules about external behavior. That is not to say that the way of Christ is only internal — one does need to give attention to how one acts in this world — but there is something missing from a person’s Christianity if it entirely revolves around laws that dictate what a person does and does not do with their bodies.
We learn today that this was certainly happening in Ephesus:
They [the false teachers] will forbid marriage, and teach people to abstain from foods which God intended to be received with thanksgiving by people who believe and know the truth. (4:3)
Sometimes we do the same, especially when talking to younger Christians. We make it seem like the task of following Jesus is all about not getting drunk, not smoking weed, and not sleeping around. Then as people get older we talk about staying away from pornography, not speeding, and not missing church. Of course, I am not suggesting that any of these are wholesome or appropriate; I simply beg us to remember there is more to the way of Christ than external rules, and limiting Christianity to external rules is action akin to the false teachers of Ephesus.
Like Paul was calling the Ephesian church to (1:5-7), like he was calling Timothy to (4:12), the way of Christ is all about “faith, love, and holiness” — all of which have external manifestations but all of which start as attitudes and desires of the heart first and foremost. According to Paul today, to forget this is the beginning of false teaching.