Mishnayos Avos Perek 1 Mishnah 2

From the remnants: From those remaining, for after they had all died, the tradition remained in his possession. He was High Priest following Ezra.

He would say: Which is to say that he was accustomed to say. And so too every (instance) of "Rabbi x says" (or) "He would say" which is in this tractate; their meaning is "He was accustomed to saying such a thing constantly."

"The world stands": The world was only created for the sake of these three things.

"on the Torah": Had Israel not received Torah, the heavens and the earth would not have been created, as is written (Jeremiah 33:25), "Were it not for my covenant day and night, also the laws of the heavens and the earth I would not have set." (Shabbat 88a)

"on the [Temple] service": The service of the sacrifices. For such have we taught in tractate Taanit, "Were it not for the groupings [involved in the sacrifices] the heavens and the earth would not have endured (Taanit 27b)." And we have found that on account of the sacrifices that Noah brought, the Holy One, blessed be He, swore that He would never bring a flood. So it is that the world stands upon the sacrifices.

"and on acts of lovingkindness": As it is written (Ps. 89:3), “The world is built up by your kindness." And lovingkindness is to regale grooms and to comfort mourners, to visit the sick and inter the dead, and the like.