He Used To Say: "If I Am Not For Myself, Who Is For Me? And If I Am Only For Myself, What Am I? And If Not Now, When?"

This teaching can be interpreted within the context of the charge to reach out to others (mishnah 12).

If I Am Not For Myself

I.e., if I do not take an active role in these efforts...

Who Is For Me?

What merit will I have? Whether or not a person involves himself, the task he was required to fulfill will be accomplished, for the good destined to be achieved in our world will not be decreased. Nevertheless, when a person does not shoulder the task destined for him, he will lack the merit he was fated to acquire.

(Sichos Shabbos Parshas Shemini, 5737)

And If I Am Only For Myself

A person may be willing to apply himself to the task before him, but "only for himself," without seeking advice or help from others. And then...

What

not who

Am I?

i.e., he falls beneath the level of humanity.

(Ibid.)

And If Not Now, When?

He must be conscious of the urgency involved, and not postpone his efforts.

(Ibid.)