Strong’s Greek
G3315 — mesiteuo
The entry below is Strong’s own definition (1890, public domain), and every verse where the word occurs.
μεσιτεύω
mesiteuo — pronounced mes-it-yoo'-o
from 3316; to interpose (as arbiter), i.e (by implication) to ratify (as surety):--confirm. see GREEK for 3316
1 occurrence in the KJV.
Hebrews 6:17
Wherein God, willing more abundantly to shew unto the heirs of promise the immutability of his counsel, confirmed it by an oath: