Ashi — "Reward," or "Right Recompense," or simply "Fortune" — was the yazata who brought to the righteous the rewards their good lives deserved. She was the personification of the principle that the good deed is repaid; that the man who follows Asha (Truth) does not labor in vain, but receives in proper measure both the goods of this world (cattle, children, prosperity) and the rewards of the next (paradise, the Best Existence). Her name is closely related to Asha — both come from the same Indo-Iranian root — and she is the Asha-principle in its rewarding aspect, the cosmic order's way of compensating those who serve it.

Her great Avestan hymn (Yasht 17, the Ashi Yasht, also called the Ard Yasht in some traditions) is one of the most beautiful in the corpus. It describes Ashi as a beautiful maiden, daughter of Ahura Mazda and Spenta Armaiti, sister of the Amesha Spentas; she dwells on a high mountain, riding in a chariot, descending to bestow her gifts on those who deserve them. The hymn catalogs the categories of people whom Ashi rewards (the priests, the warriors, the cultivators, the artisans, the children of righteous parents) and those whom she withholds her favor from (those who have not produced offspring, those who have lived in idleness, those who have followed the lie). The catalog is one of the few in Iranian religious literature to focus directly on the social and economic dimensions of righteous living.

Ashi's reward was both material and spiritual. To the righteous in this life, she gave wealth, fertility, abundance — the visible signs of divine favor. To the righteous after death, she gave the rewards of paradise. The doctrine that prosperity in this life is a sign of righteousness, and that righteousness is the path to prosperity, was distinctively Zoroastrian in its early forms; the doctrine that righteousness is its own reward and that material success is irrelevant came later (and, when it came, came under the influence of more austere religious philosophies). In the original Avestan religion, Ashi's rewards were to be sought and enjoyed; the prosperity of the world was the gift of Ahura Mazda, mediated through her, to the souls who served him.