“Do not be carried about with various and strange doctrines. For it is good that the heart be established by grace, not with foods which have not profited those who have been occupied with them” (Hebrews 13:9).
In this closing section of the Hebrew letter, the writer realizes some Jews who have been converted to Jesus are discouraged in their new faith; so, he makes yet one more effort to try to persuade them not to leave Him and go back to the Law of Moses nor to be influenced by any other doctrine they might hear of.
The writer has just made the point that Jesus will remain the same as the Savior of the world until the end of time; thus, they should not mix the doctrine of Christ with other doctrines. “Heart” means the will of the Christian, and “grace” essentially refers to the system of grace under which the Christian lives. Then the writer refers to “foods,” referring to trying to mix some of the ceremonial requirements of the Old Law with the new law of Christ.
This verse is a re-enforcement of the point made in the previous verse about Jesus remaining the same forever. We, under Jesus, are not at liberty to change His doctrine nor to mix elements of another doctrine with His. Jesus is all we need.