Some information about the Sufi, mathematician and poet Omar Khayyam is here. In this quatrain, the ‘hands of Moses’ is a reference to a verse in the Book of Exodus in which Moses puts his hand into his cloak and brings it forth ‘white as snow.’ Here it describes the branches of fruit trees covered with white blossoms. The ‘thrusting corn’ (or grain) is drawn upward by the breath of Jesus because he had the power to raise the dead from the earth.

The sweet Spring-breezes now the world adorn,
In hope of rain its eyes salute the morn;
The hands of Moses whiten many a spray,
The breath of Jesus moves the thrusting corn.

Translation Arthur B. Talbot