The rain water that falls from the sky is gathered from many sources of water on earth. These sources vary from pious Ganges (purest) to small ditches (most impure). All the rain water is collected as the oceans (a symbol of group evolution) and participates in forming the rain cloud that is purest form of water. All this gathering of water helps nourish the various seeds (the egos that are incarnating). But a seed can't evolve until it is planted at the appropriate depth with in the bosom of earth. Similarly the Ego (the seed in evolution) which are planted in the bodies physical, emotional, mental etc., need the rain of DIVINE WISDOM to evolve.