Oecumenius — on Rev 6:12 (Commentary on Revelation)

“The breaking of the sixth seal accomplished the perfect completion of our salvation; it destroyed death; it restored life; it crowned the conqueror of mankind, triumphing with confidence according to what is written: "For the only-begotten ascended on high; he led captivity captive; he received gifts among men." (Ps. 68:18: Eph. 4:8) What then is the sixth seal's opening? It is the cross of the Lord and His death, followed by the prayer of every intellectual and sensible creature, the resurrection and ascension, "which He inaugurated for us a new and living way," the return from death to life through the tearing of "the veil of His flesh" (Heb. 10:20); which benefited not only the living but also those who had gone before. For the Lord also went and preached to those in Hades who had once disobeyed, according to the divine apostle Peter, (1 Peter 3:19-20) and saved those who believed there, as is also thought by Cyril. Of which things having happened, a great earthquake occurred, he says, and the sun became black as sackcloth made of hair, and the whole moon became blood, and the stars of the sky fell to the earth, like a fig tree casting its unripe figs when shaken by a strong wind. The vision clearly depicts for us the signs that occurred on the cross: the earthquake and the shaking of the earth (Matt. 27:51), the darkening of the sun, and the entire transformation of the moon into blood. Indeed, the whole [ὅλη] was added very precisely to the moon; for being nearly full and not divided, it showed the entire suffering on the day of the crucifixion through its entirety. It is customary for the enlightened part for such things to occur during lunar eclipses. And these things the prophet Joel also foretold would happen, saying, "The sun shall be turned into darkness, and the moon into blood, before the great and glorious day of the Lord comes." (Joel 2:31)”