All things bear record · Doctrine and Covenants
1 witness of Christ here, and 1 further echo from the reading.
Behold and hearken, O ye elders of my church, who have assembled yourselves together, whose prayers I have heard, and whose hearts I know, and whose desires have come up before me. Doctrine and Covenants 67:1–4
The Lord who hears prayers and holds heaven and earth in His hands bears His own testimony that the revelations are true.
I AM — the covenant name of Jehovah, the self-existent One
And again, verily I say unto you that it is your privilege, and a promise I give unto you that have been ordained unto this ministry, that inasmuch as you strip yourselves from jealousies and fears, and humble yourselves before me, for ye are not sufficiently humble, the veil shall be rent and you shall see me and know that I am—not with the carnal neither natural mind, but with the spiritual. Doctrine and Covenants 67:10–12
Christ promises humble servants they will see Him and know that He lives, though only through the Spirit changing them. "Know that I am" echoes His divine name I AM.
How we know: the verse itself names Him · a Church study aid lists it