Who is the "I"?

Rabbi Yehoshua ben Levi said (Daf Yomi: Gittin 39a) : They asked before Rebbe: What is the law if someone says that he gives up hope of ever retrieving his slave? Rebbe replied: I say that such a slave can only be fixed (to marry) with a document.

Many times in Shas, it is found that Rebbe used this terminology, “I say etc.” What was his intention with these words?

Reb Yosef Engel in Beis Haotzar explains that it is known that Rebbe was a tremendously humble person. The Gemora in Sotah (49a) states that when Rebbe died, humility ceased. Perhaps what Rebbe was saying was that it appears to him that the halachah is like this-and-this, but not that it is most definitely so.

He also writes that it is clear from the seforim of the students of the Baal Shem Tov that lofty people are constantly thinking that their words and actions are not emanating from their own power and strength; rather, it is all coming from the Ribbono shel Olam. In kabbalah, the Shechinah is referred to as “Ani,” “I.” This is the explanation in the Gemora Sukkah (53a) when Hillel said, “If I am here, then everyone is here.” The “I” did not refer to himself, for Hillel, we also know was extremely humble. Rather, he was referring to the Shechinah. This, perhaps, is what Rebbe was saying when he said, “I say.” The Shechinah which is inside of me is saying that the halachah is like this.