Tertullian (c. 150 – c. 229), a former Roman soldier and a lawyer, was converted to Christ when he was about forty. He became a dedicated advocate for Christianity against paganism. In this letter to his wife, he outlines many of the blessings enjoyed by two believers, joined together in marriage.
What kind of yoke is that of two believers, partakers of one hope, one desire, one discipline, one and the same service? Both are brethren, both fellow servants, no difference of spirit or of flesh; nay, they are truly “two in one flesh.” Where the flesh is one, one is the spirit too. Together they pray, together they prostrate themselves; together perform their fasts; mutually teaching, mutually exhorting; mutually sustaining . . . Between the two echo psalms and hymns; and they mutually challenge each other which shall better chant to their Lord. Such things when Christ sees and hears, He joys.1
1 Tertullian, Elucidations, in The Ante-Nicene Fathers, vol. 4, eds. Alexander Roberts and James Donaldson (Grand Rapids: Wm. B. Eerdmans, 1956), 48. Punctuation simplified. In other translations see Elucidations, Book II, Chap. VIII.