Rabbi Yosef Yitzchak Schneersohn (1880-1950), the sixth rebbe of Chabad-Lubavitch, once told:

Once, after returning from a walk with my father,1 he reminded me of a spot we passed---a busy street corner. "At that spot," he said to me, "I suddenly had an extremely rich and inspiring thought. I imagine that this is because a Jew once prayed minchah (the afternoon prayer) at this spot."

That Jew probably prayed with half a mind, disturbed and jostled by the traffic on this busy street. Yet the holy words of prayer purified the air so that when father passed that spot many years later, his sensitive mind was stimulated to generate an especially pure and refined idea.