"Every vigil celebrated in the Lord's honor is pleasing to God and acceptable to him, but this particular vigil more than all the rest. That is why this night in particular holds the title The Lord's Vigil. Indeed, what we read is: 'All the Israelites must keep a vigil for the Lord' (Ex 12,42). And this night well merits the title since the Lord awoke in life that we might not remain asleep in death. For he suffered death's sleep for our sakes in the mystery of his Passion, yet this sleep of the Lord has become the vigil of the whole world because the death of Christ has removed the sleep of eternal death from us. He himself says it through the prophet: 'I lie down in sleep, I wake again, and my sleep was sweet to me' (Ps 3,6; Jer 31,26). This sleep of Christ's that we have called to mind, from the bitterness of death to the sweetness of life, cannot be anything but sweet.
Solomon wrote: 'I sleep but my heart is awake' (Sg 5,2). These words seemingly show the mystery of the divinity and flesh of the Lord. He slept according to the flesh but his divinity kept watch since the divinity cannot sleep...: 'He neither slumbers nor sleeps, the guardian of Israel' (Ps 121,4)... He slept according to the flesh but his divinity visited hell in order to draw out the man whom it had held captive. Our Lord and Savior desired to enter into every place to have mercy on everyone. He came down from heaven to the earth to visit the world, and again he descended from earth to hell to carry light to those held captive there, as spoken by the prophet: 'Upon those who dwelt in the land of gloom a light has shone' (Is 9,1).
Hence angels in heaven, men on earth and the souls of the faithful in the dwelling place of the dead celebrate this vigil of the Lord... If one sinner's repentance, as the Gospel says, gives joy to the angels in heaven (Lk 15,7.10), how much more the redemption of the whole world?... And so, this vigil is not just a feast for men and angels but also for the Father, the Son and the Holy Spirit, because the world's salvation is the Trinity's happiness."
-Saint Chromatius of Aquileia, 1st Sermon for the Paschal Vigil