If I am not for myself, who is for me?When I am for myself, what am I?If not now, when?

: "If I am not for myself, who is for me?
When I am for myself, what am I?
If not now, when?
�Hillel"

Worth the whole commentary:

Commentary [1:14]
Today Hillel’s famous three questions are usually taken rhetorically, meaning: Look out for yourself, stick up for yourself, or no one else will; but if you are only concerned for your own selfish interests, you are unworthy; and now is the time to act.

Rabbinic commentators give a similar but more pious interpretation: only I can carry out my responsibilities to do good, and get merits by which God will judge me when I die. Maimonides adds psychological insight: a person acquires habits of doing right or wrong—virtues and vices—while young; youths should do good deeds now, and not wait until adulthood.

Hillel put these sayings in the form of questions, I believe, because he intended them to be asked and answered when we face important decisions.

If I am not for myself, who is for me? not only implies that it is legitimate to pursue your own interests, but also starts you thinking of the best way to pursue your interests. Your answer to “If I were not for myself—if I had to rely totally on others—who would be for me?” will give you a shrewd idea of who are your friends and allies, and who is not with you, or is actively opposed to your efforts.
When I am for myself, what am I? asks “What should be my role in this situation?” This partly a moral question: what do I owe to others, what do they owe to me? And it is also a practical question: how should we define and share responsibilities in a way that is most beneficial to both people in a relationship?

If not now, when? is the strategic question of timing. Sometimes, we should act immediately, and sometimes we should wait until a later, more opportune moment. What is urgent? What should I postpone? What can I do now to improve my options later?

Hillel’s three questions encapsulate a philosophy of life which is a true synthesis of the ancient Hebrew and ancient Greek traditions—a synthesis at the heart of Classical Judaism. In contrast to the Greek tradition, Hillel doesn’t begin just with personal happiness as the goal, and then try to see how wisdom can lead a person to the path of goodness. And in contrast to the Hebrew tradition, he doesn’t begin just with a person’s responsibilities to others and to the community.

Hillel’s approach instead is a conscious effort to balance the pursuit of self-interest and service to others. He sees that balancing our personal interests and our obligations to others is a problem that each of us needs to solve creatively at each stage of our lives. Each time we face an important life decision, the three questions launch us and guide us on this quest for balance.