“It becomes logical to ask where the idea originates that the rules of the game of life ought to be such that those who are weak, disabled or ill should be helped?
One answer is obvious: this is the game typically played in childhood. Every one of us was, at one time, a weak and helpless child, cared for by adults: without such help we would not have survived and become adults.
Another, almost equally obvious answer is that the prescription of a help-giving attitude toward the weak is embodied in the dominant religions of Western man.
Judaism, and especially Christianity, teach these rules by means of parable and prohibition, example and exhortation, and by every other means available to their representatives.”

Speech made in honor of Thomas Mann in January 1939, when Mann was given the Einstein Prize given by the Jewish Forum. Quoted in Einstein Lived Here by Abraham Pais (1994), p. 214 http://books.google.com/books?id=u_9QAAAAMAAJ&q=%22becomes+lack+of+power%22#search_anchor
1930s
Context: The standard bearers have grown weak in the defense of their priceless heritage, and the powers of darkness have been strengthened thereby. Weakness of attitude becomes weakness of character; it becomes lack of power to act with courage proportionate to danger. All this must lead to the destruction of our intellectual life unless the danger summons up strong personalities able to fill the lukewarm and discouraged with new strength and resolution.

Source: City of Heavenly Fire

Nobel Banquet speech, 2001

Source: Unless You Become Like This Child

Introduction, sect. 6
La poétique de la rêverie (The Poetics of Reverie) (1960)

Mr. Spencer
Source: The Catcher in the Rye (1951), Chapter 2

On Human Nature (1978), Ch.3 Development

"That Two Heads are Better than One".
Sketches from Life (1846)

Variant: It is one of the beautiful compensations of life that no man can sincerely try to help another without helping himself.