“Do not be led away by diverse and strange teachings, for it is good for the heart to be strengthened by grace, not by foods, which have not benefited those devoted to them” (Hebrews 13:9 ESV).
One commentator offers a helpful synopsis of the issue raised in Hebrews 13:9…
“Evidently one of the ‘strange’ teachings, prevalent when this letter originated, was that eating certain foods, or abstinence from certain foods, resulted in greater godliness (cf. Col. 2:16; 1 Tim. 4:1-5). This was, of course, what Judaism taught too. Judaism taught that eating food ‘strengthened the heart,’ in the sense that when the Jews ate, they also gave thanks to God, and thus brought Him into their experience (cf. Ps. 104:14-15). [a] However, Jesus’ death on the cross is the source of both the saving, and the sustaining, ‘grace of God,’ by which we experience strengthening.” (1)
Paul the Apostle also addressed this subject in the Biblical book of 1 Corinthians…
“But food does not commend us to God; for neither if we eat are we the better, nor if we do not eat are we the worse” (1 Corinthians 8:8).
We should also note our author’s subtle aside in this passage: “…those who obey these rules have not been helped by them” (GNT). Jesus explained why those who adhered to such restrictions failed to receive a benefit from them…
“‘The food that you put into your mouth doesn’t make you unclean and unfit to worship God. The bad words that come out of your mouth are what make you unclean.’
After Jesus and his disciples had left the crowd and gone into the house, they asked him what these sayings meant. He answered, ‘Don’t you know what I am talking about by now? You surely know that the food you put into your mouth cannot make you unclean. It doesn’t go into your heart, but into your stomach, and then out of your body.” By saying this, Jesus meant that all foods were fit to eat.
Then Jesus said: ‘What comes from your heart is what makes you unclean. Out of your heart come evil thoughts, vulgar deeds, stealing, murder, unfaithfulness in marriage, greed, meanness, deceit, indecency, envy, insults, pride, and foolishness. All of these come from your heart, and they are what make you unfit to worship God'” (Mark 7:15-23 CEV).
Our final commentary ties these ideas together…
“Legislation concerning clean and unclean foods was designed to produce ritual cleanness. But this is not the same thing as inward holiness. A man might be ceremonially clean and yet be filled with hatred and hypocrisy. Only God’s grace can inspire and empower believers to live holy lives. Love for the Savior who died on account of our sins motivates us to ‘live soberly, righteously, and godly in the present age’ (Tit 2:12). After all, endless rules concerning foods and drinks have not profited their adherents.” (2)
(1) [a] William L. Lane, Word Biblical Commentary series. Dallas: Word Books, 1991, Hebrews 9—13, pp. 533-36, quoted in, Constable, Thomas. DD, Notes on Hebrews 2023 Edition “Instructions regarding religious duties 13:7-19” [13:9] https://www.planobiblechapel.org/tcon/notes/html/nt/hebrews/hebrews.htm
(2) William Macdonald, Believer’s Bible Commentary Edited by Arthur Farstad, Thomas Nelson Publishers [13:9]