What sentence in Chapter 60 did prove that Father Damaso is the father of Maria Clara?

From the text:

And when the young man whispered a name in his ear, only Ibarra could hear it.

—¿Anó ang aking magagawâ? Should my love trample on the memory of my mother, the pride of my father and the honor of my real father? Can I do this without you being the first to devalue me?

"But the evidence, was there any evidence?" You need proof! - Chrysostom said suddenly, as if being slapped.

The girl pressed the two papers to her chest.

—Here are two letters from my mother, two letters printed in the middle of the high cry of her own conscience at the time she was still in her womb. Accept it and read it, and you will see how he cursed me and longed for me to die ..., my death which was not agreed upon, even though my father insisted, by means of drugs! These letters were forgotten when my father, in the house where he lived, was taken by that man and kept, and only given to me when he exchanged your letter ..., not because he was supposed to be able to read.Páhiná hindi acó pacácasal sa iyó cung walang capahintulutan ang aking amá. As soon as I carried the two letters that had been the capital of your letter, I felt a coldness in my heart. I have ruined you, I have ruined my darling .... What can a daughter not do after the recovery of a dead mother and two living fathers? Can I even guess where your letter will be used?

Ibarra sighed. María Clara continues:

—¿Anó pa ang nálalabi sa akin? Can I tell you who my father is, can I tell you who apologized to him, who is still your son for what he has suffered so much? Can I tell my father to forgive you, can I tell him that I am his son, that he still longs for my death? I have nothing left but patience, I will keep the secret to myself and die in grief! ... Now, my friend, now that you know the life of your poor María, will you be able to bring more? to his dismissal of that precious smile?