Q. What Is Meant by Fulfilling All Righteousness Ans. I Believe He Is Looking Unto the Cross Which Is the Full Expression of What He Does Here, Identifying Himself With Sinners in Their Need; and As He Says, "Therefore Cloth My Father Love Me Because I Lay Down My Life," the Father's Voice Here Proclaims Him His Beloved Son

"Burying" is putting the dead out of sight, and this that "as Christ was raised up from the dead, even so we also should walk in newness of life." The glory of the Father required that He should be so raised up. " Newness of life " is life of a new kind. God deals with all the evil in us by death, and buries it that we may be free for this new life.
In Romans we are seen as dead with Christ, not risen. In Ephesians we are seen as risen with Christ, not dead. In Colossians we are seen as both dead and risen, linking both together.
Death, with God, is His clearing away of the old thing to bring in what is new. Verse 5 shows that death involves resurrection.
"Verse 6. Knowing this that "our old man," etc. This " old man," I believe, is Pharaoh. It is well to distinguish the terms here. The flesh is the old nature. When Scripture wants to speak of what characterizes the flesh, it speaks of "sin in the flesh." Sin is the principle of evil which makes it what it is. Here it is the " old man," not the old nature, or the evil principle; but myself as I was, as I am by nature.
People speak of crucifixion as a lingering Here, however, it is a thing done-" our old man is crucified" and with Christ, dead long ago.
" The body of sin " is sin in the lump, as we say. " Might be destroyed " should be, rather, annulled. This is my deliverance from captivity, just as Israel at the Red Sea.
People might have thought that God would have put arms into Israel's hands to fight with Pharaoh, instead He leads them through the sea-death. The border of Egypt, and the death they passed through untouched, is the end of their enemy.