Romans 4:13 For the promise that he would be the heir of the world was not to Abraham or to his seed through the law, but through the righteousness of faith. 14 For if those who are of the law are heirs, faith is made void and the promise made of no effect, 15 because the law brings about wrath; for where there is no law there is no transgression.

I once heard John Bevere teach on pursuing holiness. It’s not about what is wrong or right. It is about seeking God with your whole heart. It is about loving what He loves. When we strive to find the proverbial line, we have already missed the point.
We are heirs to the promise because we believe in God and we love Him, and through that relationship we become sons and daughters.

There is sin that is not the “crossing the line” of the Law of Moses. The root of sin isn’t in breaking the law, but in breaking trust with God; with denying His loving, caring purpose in every command He gives. Before Adam sinned he broke trust with God – therefore God’s plan of redemption is centered on a relationship of trusting love – faith – instead of law-keeping. When we center our relationship with God on law-keeping instead of trusting love, we go against His whole plan.