Where in God, willing more abundantly to shew unto the heirs of promise the immutability of his counsel, confirmed [it] by an oath:
Berean Study Bible (BSB) - Hebrews 6:17 >So when God wanted to make the unchanging nature of His purpose very clear to the heirs of the promise, He guaranteed it with an oath.
Textus Receptus (TR) - Hebrews 6:17 >Ἐν ᾧ περισσότερον βουλόμενος ὁ Θεὸς ἐπιδεῖξαι τοῖς κληρονόμοις τῆς ἐπαγγελίας τὸ ἀμετάθετον τῆς βουλῆς αὐτοῦ, ἐμεσίτευσεν ὅρκῳ,