Translated by Ch. Browne and J. Swallow.
III. Concerning two of these births, the first and the last, we have not to speak on the present occasion. Let us discourse upon the second, which is now necessary for us, and which gives its name to the Feast of the Lights. Illumination is the splendour of souls, the conversion of the life, the question put to the Godward conscience.  It is the aid to our weakness, the renunciation of the flesh, the following of the Spirit, the fellowship of the Word, the improvement of the creature, the overwhelming of sin, the participation of light, the dissolution of darkness. It is the carriage to God, the dying with Christ, the perfecting of the mind, the bulwark of Faith, the key of the Kingdom of heaven, the change of life, the removal of slavery, the loosing of chains, the remodelling of the whole man. Why should I go into further detail? Illumination is the greatest and most magnificent of the Gifts of God. For just as we speak of the Holy of Holies, and the Song of Songs, as more comprehensive and more excellent than others, so is this called Illumination, as being more holy than any other illumination which we possess.
IV. And as Christ the Giver of it is called by many various names, so too is this Gift, whether it is from the exceeding gladness of its nature (as those who are very fond of a thing take pleasure in using its name), or that the great variety of its benefits has reacted for us upon its names. We call it, the Gift, the Grace, Baptism, Unction, Illumination, the Clothing of Immortality, the Laver of Regeneration, the Seal, and everything that is honourable. We call it the Gift, because it is given to us in return for nothing on our part; Grace, because it is conferred even on debtors; Baptism, because sin is buried with it in the water; Unction, as Priestly and Royal, for such were they who were anointed; Illumination, because of its splendour; Clothing, because it hides our shame; the Laver, because it washes us; the Seal because it preserves us, and is moreover the indication of Dominion. In it the heavens rejoice; it is glorified by Angels, because of its kindred splendour. It is the image of the heavenly bliss. We long indeed to sing out its praises, but we cannot worthily do so.
 This is the literal version of the passage, which is somewhat loosely quoted from 1 S. Peter iii. 21, where the A.V. renders "the answer of a good conscience towards God," and the R.V., "The interrogation (Marg. inquiry) of a good conscience, etc." The passage is usually explained as referring to the Interrogatories in Holy Baptism, answered by the threefold Vow which enlists us "under Christ's banner against sin, the world, and the Devil," professes the Faith, and promises obedience.
Reference address : https://www.elpenor.org/gregory-nazianzen/holy-baptism.asp?pg=2