Alcuin
Catena Aurea · Johannesevangelium 3
—and no man receiveth his testimony. He that hath received his testimony hath set to his seal that God is true. For he whom God hath sent speaketh the words of God: for God giveth not the Spirit by measure unto him. The Father loveth the Son, and hath given all things into his hand. He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.
Or, Hath put to his seal, i. e. hath put a seal on his heart, for a singular and special token, that this is the true God, Who suffered for the salvation of mankind.