Victorinus of Pettau

Now is manifested the reason of the truth why the fourth day is called the Tetras, why we fast even to the ninth hour, or even to the evening, or why there should be a passing over even to the next day. Therefore this world of ours is composed of four elements-fire, water, heaven, earth. These four elements, therefore, form the quaternion of times or seasons. The sun, also, and the moon constitute throughout the space of the year four seasons-of spring, summer, autumn, winter; and these seasons make a quaternion. And to proceed further still from that principle, lo, there are four living creatures before God's throne, four Gospels, four rivers flowing in paradise; four generations of people from Adam to Noah, from Noah to Abraham, from Abraham to Moses, from Moses to Christ the Lord, the Son of God; and four living creatures, viz., a man, a calf, a lion, an eagle; and four rivers, the Pison, the Gihon. the Tigris, and the Euphrates. The man Christ Jesus, the originator of these things whereof we have above spoken, was taken prisoner by wicked hands, by a quaternion of soldiers. Therefore on account of His captivity by a quaternion, on account of the majesty of His works,-that the seasons also, wholesome to humanity, joyful for the harvests, tranquil for the tempests, may roll on,-therefore we make the fourth day a station or a supernumerary fast.