Haymo of Halberstadt
Catena Aurea · Johannesevangelium 3
Nicodemus answered and said unto him, How can these things be? Jesus answered and said unto him, Art thou a master of Israel, and knowest not these things? Verily, verily, I say unto thee, We speak that we do know, and testify that we have seen; and ye receive not our witness. If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things.
(Hom. in Oct. Pent.) Why, it is asked, does He speak in the plural number, We speak that we do know? Because the speaker being the Only-Begotten Son of God, He would shew that the Father was in the Son, and the Son in the Father, and the Holy Ghost from both, proceeding indivisibly.