Hebrews 6:17

17inἐνwhichᾧmore abundantlyπερισσότερονdesiringβουλόμενοςὁGodθεὸςto showἐπιδεῖξαιto theτοῖςheirsκληρονόμοιςof theτῆςpromiseἐπαγγελίαςtheτὸunchangeablenessἀμετάθετονof theτῆςpurposeβουλῆςof Himαὐτοῦguaranteed [it]ἐμεσίτευσενby an oathὅρκῳ,

in which God, willing to show more abundantly the unchangeableness of His purpose to the heirs of the promise, guaranteed [it] by an oath,