Swami Vivekananda , Conversation with disciples.

Even the least work done for others awakens the power within; even
thinking the least good of others gradually instills into the heart
the strength of a lion. I love you all ever so much, but I wish you
all to die working for others--I should rather be glad to see you do
that!

Conversation with Priya Nath Sinha. Recorded in Bengali. Complete Works, 5: 382