John 4:25-26
“I know that Messias comes, which is called Christ: when He has come, He will tell us all things. Jesus says unto her, I am that speak unto you.”
And whence came the Samaritans to expect the coming of Christ, seeing that they received Moses only? From the writings of Moses themselves. For even in the beginning He revealed the Son. “Let Us make man in Our Image, after Our Likeness”, was said to the Son. It was He who talked with Abraham in the tent. And Jacob prophesying concerning Him said, “A ruler shall not fail from Judah, nor a leader from his thighs, until He come for whom it is reserved, and He is the expectation of nations.” And Moses himself says, “The Lord your God will raise up unto you a Prophet of your brethren like me, unto Him shall you hearken.” And the circumstances attending the serpent, and the rod of Moses, and Isaac, and the sheep, and many other things they who chose might select as proclaiming His coming.
“And why, pray,” says one, “did not Christ lead on the woman by these means? Why did He instance the serpent to Nicodemus, and mention prophecy to Nathanael, but to her say nothing of the kind? For what reason, and why?” Because they were men, and were versed in these things, she a poor ignorant woman unpracticed in the Scriptures. Wherefore He does not speak to her from them, but draws her on by the “water” and by prophecy, and brings her to make mention of Christ and then reveals Himself; which had He at first told the woman when she had not questioned Him, He would have seemed to her to trifle and talk idly, while as it is by bringing her little by little to mention Him, at a fitting time He revealed Himself. To the Jews, who continually said, “How long dost Thou make us to doubt? Tell us if You are the Christ”, to them He gave no clear answer, but to this woman He said plainly, that He is. For the woman was more fair-minded than the Jews; they did not enquire to learn, but always to mock at Him, for had they desired to learn, the teaching which was by His words, and by the Scriptures, and by His miracles would have been sufficient. The woman, on the contrary, said what she said from an impartial judgment and a simple mind, as is plain from what she did afterwards; for she both heard and believed, and netted others also, and in every circumstance we may observe the carefulness and faith of the woman.
Source: Homilies on the Gospel of John (New Advent)