As Khenpo Kunzang Pelden explains in his commentary on Shantideva’sWay of the Bodhisattva:
Precious bodhichitta, which is endowed with such extraordinary qualities, does not arise in the absence of causes and conditions. All the causes for it must be complete. . . Now the best of all ways of accumulating merit is to make offerings; moreover, the presentation of perfect offerings has the effect of rendering one’s mind pure and lucid.
The practice of water offerings in the Tibetan Buddhist tradition can be traced back to the 11th century whenAtiśa first arrived in Tibet:
The Tibetan landscape made him think that one could accumulate limitless merit by simply offering water to the Three Jewels using the pure ground water so readily available. This is because water is unlike any other offering substance, for rich and poor alike can relinquish water more easily than any other offering substance. It can be offered without regret, untainted by stinginess and the like, for the sake of merit and virtue.