Unchangeable

Vine's Expository Dictionary of NT Words

1: ἀπαράβατος (Strong'S #531 — Adjective — aparabatos — ap-ar-ab'-at-os )

is used of the priesthood of Christ, in  Hebrews 7:24 , "unchangeable," "unalterable, inviolable," Rv, marg. (a meaning found in the papyri); the more literal meaning in Av and Rv margins, "that doth not pass from one to another," is not to be preferred. This active meaning is not only untenable, and contrary to the constant usage of the word, but does not adequately fit with either the preceding or the succeeding context.

King James Dictionary

Unchangeable, a. Not capable of change immutable not subject to variation. god is an unchangeable being.