Wherein God, willing more abundantly to shew unto the heirs of promise the immutability of his counsel, confirmed it by an oath:
Because God wanted to make the unchanging nature of his purpose very clear to the heirs of what was promised, he confirmed it with an oath.
Ἐν ᾧ περισσότερον βουλόμενος ὁ Θεὸς ἐπιδεῖξαι τοῖς κληρονόμοις τῆς ἐπαγγελίας τὸ ἀμετάθετον τῆς βουλῆς αὐτοῦ, ἐμεσίτευσεν ὅρκῳ,
En ō perissoteron boylomenos o Theos epideixai tois klēronomois tēs epaggelias to ametatheton tēs boylēs aytoy, emesiteysen orkō,