As, however, examples always render an argument more vivid to the hearers, I propose to instruct the mind of the blasphemers by an illustration, explaining, by means of earthly and lowly matters, those matters which are great, and invisible to the senses. If it befell you to be enduring the misfortune of captivity among enemies, to be in bondage and in misery, to be groaning for that ancient freedom which thou once had— and if all at once three men, who were notable men and citizens in the country of your tyrannical masters, set you free from the constraint that lay upon you, giving your ransom equally, and dividing the charges of the money in equal shares among themselves, would you not then, meeting with this favour, look upon the three alike as benefactors, and make repayment of the ransom to them in equal shares, as the trouble and the cost on your behalf was common to them all— if, that is, thou were a fair judge of the benefit done to you? This we may see, so far as illustration goes, for our aim at present is not to render a strict account of the Faith. Let us return to the present season, and to the subject it sets before us.
I find that not only do the Gospels, written after the Crucifixion, proclaim the grace of Baptism, but, even before the Incarnation of our Lord, the ancient Scripture everywhere prefigured the likeness of our regeneration; not clearly manifesting its form, but fore-showing, in dark sayings, the love of God to man. And as the Lamb was proclaimed by anticipation, and the Cross was foretold by anticipation, so, too, was Baptism shown forth by action and by word. Let us recall its types to those who love good thoughts— for the festival season of necessity demands their recollection.
Hagar, the handmaid of Abraham (whom Paul treats allegorically in reasoning with the Galatians), being sent forth from her master's house by the anger of Sarah— for a servant suspected in regard to her master is a hard thing for lawful wives to bear— was wandering in desolation to a desolate land with her babe Ishmael at her breast. And when she was in straits for the needs of life, and was herself near unto death, and her child yet more sore for the water in the skin was spent (since it was not possible that the Synagogue, she who once dwelt among the figures of the perennial Fountain, should have all that was needed to support life), an angel unexpectedly appears, and shows her a well of living water, and drawing thence, she saves Ishmael. Behold, then, a sacramental type: how from the very first it is by the means of living water that salvation comes to him that was perishing— water that was not before, but was given as a boon by an angel's means. Again, at a later time, Isaac— the same for whose sake Ishmael was driven with his mother from his father's home— was to be wedded. Abraham's servant is sent to make the match, so as to secure a bride for his master, and finds Rebekah at the well: and a marriage that was to produce the race of Christ had its beginning and its first covenant in water. Yes, and Isaac himself also, when he was ruling his flocks, dug wells at all parts of the desert, which the aliens stopped and filled up, for a type of all those impious men of later days who hindered the grace of Baptism, and talked loudly in their struggle against the truth. Yet the martyrs and the priests overcame them by digging the wells, and the gift of Baptism over-flowed the whole world. According to the same force of the text, Jacob also, hastening to seek a bride, met Rachel unexpectedly at the well. And a great stone lay upon the well, which a multitude of shepherds were wont to roll away when they came together, and then gave water to themselves and to their flocks. But Jacob alone rolls away the stone, and waters the flocks of his spouse. The thing is, I think, a dark saying, a shadow of what should come. For what is the stone that is laid but Christ Himself? For of Him Isaiah says, “And I will lay in the foundations of Sion a costly stone, precious, elect:” and Daniel likewise, “A stone was cut out without hands,” that is, Christ was born without a man. For as it is a new and marvellous thing that a stone should be cut out of the rock without a hewer or stone-cutting tools, so it is a thing beyond all wonder that an offspring should appear from an unwedded Virgin. There was lying, then, upon the well the spiritual stone, Christ, concealing in the deep and in mystery the laver of regeneration which needed much time— as it were a long rope— to bring it to light. And none rolled away the stone save Israel, who is mind seeing God. But he both draws up the water and gives drink to the sheep of Rachel; that is, he reveals the hidden mystery, and gives living water to the flock of the Church. Add to this also the history of the three rods of Jacob. For from the time when the three rods were laid by the well, Laban the polytheist thenceforth became poor, and Jacob became rich and wealthy in herds. Now let Laban be interpreted of the devil, and Jacob of Christ. For after the institution of Baptism Christ took away all the flock of Satan and Himself grew rich. Again, the great Moses, when he was a goodly child, and yet at the breast, falling under the general and cruel decree which the hard-hearted Pharaoh made against the men-children, was exposed on the banks of the river— not naked, but laid in an ark, for it was fitting that the Law should typically be enclosed in a coffer. And he was laid near the water; for the Law, and those daily sprinklings of the Hebrews which were a little later to be made plain in the perfect and marvellous Baptism, are near to grace. Again, according to the view of the inspired Paul, the people itself, by passing through the Red Sea, proclaimed the good tidings of salvation by water. The people passed over, and the Egyptian king with his host was engulfed, and by these actions this Sacrament was foretold. For even now, whenever the people is in the water of regeneration, fleeing from Egypt, from the burden of sin, it is set free and saved; but the devil with his own servants (I mean, of course, the spirits of evil), is choked with grief, and perishes, deeming the salvation of men to be his own misfortune.
Source: On the Baptism of Christ (Sermon for the Day of Lights) (New Advent)