Jesus Christos (Messiah) is unchanging (immutable). He will always be the same from yesterday to now and into the expanse of eternity.
“Yesterday, today, and tomorrow” was written to emphasize and provide an example of just how unchanging Jesus is. He existed before creation. Jesus came to earth to live among us and die for us. He is with us now giving what we need and more, guiding us, and protecting us. Jesus will exist into infinity. He is part of the Godhead. No matter what conflicting teachings and doctrines you hear, the Jesus who has always been and will always be—the One you met when you were convicted of your sins and when you recognized you need a Savior—is the unchanging Jesus Christ.
This truth is what the writer of Hebrews taught, reinforced, and emphasized in this verse.
So, “Do not be carried away by all kinds of strange teachings, for it is good for the heart to be strengthened by grace and not by foods of no value to those devoted to them” (Hebrews 13:9). Ceremony (rituals, food, clothes, words, etc) have no value for the people who follow them. Jesus, His grace, His teaching, and His examples should be what we believe and follow.
Don’t follow those who teach, preach, and model a way different from Jesus. Theirs is for vanity and pride. It serves only the false teacher and not his/her hearers. Jesus and His words are unchanging.
Lord Jesus, help me not to be confused by conflicting teachings. Help me to see You alone and Your path. Lead me in the paths of Your righteousness for Your glory, O Lord. Help me not to fear evil but to see You are with me. You are my Foundation, my Savior. You alone are unchanging. You alone, Jesus, are the Truth and Way. Lead me in it. .