Hebrew 13:9-10 Do not be led away by diverse and strange teachings, for it is good for the heart to be strengthened by gracenot by foods, which have not benefited those devoted to them. 
The writer of Hebrews is conveying to these Jewish believers, that living a godly life by distinguishing what “foods” you should and should not eat is pointless, if the focus of your life is not in grace through Jesus Christ.  However, it is easier to understand the Jewish struggle of religious works in what “foods to eat”, to the grace we Christians live in today.  The Jews had the Old Testament that had written food laws of what is godly and what is not, and followed it for centuries!  But we as modern Christians establish things as godly that have no biblical basis at all.  Why is that?
The passage says to be “strengthened by grace”, which yields all credit to Christ, but self-righteousness always wants “a hand” in taking credit.  We like to add things, so instead of giving Christ all the credit, we can say it had something to do with how we did it!  Sadly what we end up doing is alienating ourselves from Christ and living for His praise, as well as not relating to people who actually seek grace to be accepted by God! (Hebrews 13:10-16)
For Christians, grace through Christ is what unifies us to God and one another, nothing else.  If you believe that, than it is impossible not to relate to people on some kind of level.  Yet we find ways not to relate, which means we are not living to be “strengthened by grace” promoting humility, but by what we have added to distinguish us, promoting pride.  When pride rules, Christ doesn’t, and the idea of unity becomes pointless…
In His Love, Ld