Hebrews 6:17

Wherein God, being minded to show more abundantly unto the heirs of the promise the immutability of his counsel, interposed with an oath; that by two immutable things, in which it is impossible for God to lie, we may have strong encouragement, who have fled for refuge to lay hold of the hope set before us.

The two immutable things are the promise of God and the oath by which it was confirmed. Boatman noted the opinion of some that the two immutable things are

the oath made to Abraham respecting a Son, the Messiah; and the second refers to Christ's priesthood, recorded in Psalms 110:4: "Jehovah hath sworn and will not repent. Thou art a priest forever after the order of Melchizedek.[9]

It is only in an accommodative sense, however, that God's oath could be understood as any way different from his word without an oath. It was the word only that God spoke when the worlds came into existence; and the mention of God's oath does not reveal on the part of God any need whatever to make his word more sure through such a human device as an oath, but rather a heavenly regard for human opinions and practices in which God accommodated himself to the customs of people, not for his sake, but for theirs, that people might more fully and completely believe in the word of his power. This seems to be a valid deduction from the words "more abundantly" as used in the text here; and the meaning is that God went over and beyond what was necessary, and that his doing so sprang solely from his desire to demonstrate ("being minded to show") what solid ground supported faith in his eternal designs.

Who have fled for refuge refers to Christians who had sought and received refuge in Christ from all their sins and is a reference to the ancient cities of refuge in Canaan which appear in this place as a type of the refuge in Christ. Joshua 20 records the establishment of six cities of refuge: Kedesh, Shechem, Hebron, Bezer, Ramoth-Gilead, and Golan, three west of the Jordan and three on the east. Collectively, these cities stand as a type of the church, in which safety from the avenger of blood (Satan) may be received only by entering into and remaining within the sanctuary; and, although the ancient refugee was required to remain within the haven only until the death of the high priest, no such termination of residence within the church is allowed, because the Christian's High Priest lives forever.