And there are statements in Scripture which might lead one to reason that God’s definition of sin has changed over time, and even that sin no longer exists, such as, “all things are lawful for me.” (1Co 10:23) This means something, and it’s evidently very important.
The statement, by itself, could mean several different things. It could mean, for example, that God’s Law no longer applies to the author, or to certain people, or to everyone, in which case there’s no more moral law and therefore no more sin. Yet this begs asking what lawful means; in order for something to be in accordance with the law it seems there must, in fact, be a law with which to be aligned. And this we all know, that there is still a moral law, and we reveal this when others wrong us. We cannot live otherwise.
It could also mean that every thing which isn’t explicitly forbidden by God is lawful: since being contrary to God’s Law isn’t a thing for one who fears God.
The first rule of interpretation in scripture (hermeneutics) is to respect context: first the local, immediate context of the surrounding verses, then the chapter or book of the Bible containing the text, and ultimately the whole of Scripture.
In this case, the context is about eating food dedicated to idols. (19-21) The entire context is about how this is not expressly forbidden by God (1Co 8:4); dedicating food to an idol changes nothing about the food itself: it doesn’t make the food unfit to eat.
However, as the context bears out, though it may be lawful to eat food sacrificed to idols, it may not be expedient; in other words, it may not be suitable for achieving a godly purpose. If others are tempted to go against their conscience through lawful behavior, then this behavior is harmful and violates the higher law of love, even though it’s not unlawful in itself.
This second way of interpreting the text is consistent with the whole of scripture, whereas the first is not only explicitly contrary to scripture, it’s self-deception, missing the truth altogether. (1Jn 1:8)
If we’re picking and choosing texts out of context to support our position, we’re very likely heading for destruction. (2Pe 3:16) If all scripture is given by inspiration (2Ti 3:16), any interpretation must be consistent with the entire Scripture. To find the truth we must rightly divide the Word of Truth and not handle God’s Word deceitfully. (2Co 4:2)