Three the Trinity
The number three is the number of God. For God the Trinity in heaven gives witness of all things. For as it says, "For there are three that bear witness in heaven: the Father, the Word, and the Holy Spirit; and these three are one.” And these Three give witness to men on this earth. As it says, “There are three that bear witness on earth: the Spirit, the water, and the blood; and these three agree as one."