Augustine of Hippo

"Who sends His crystal like morsels of bread" [Psalm 147:17]. We need not spend our toil again in saying what crystal is. We have already said it, and I do not think that you, beloved, have forgotten it. What is then, "He sends His crystal like morsels of bread"? What is "crystal"? It is very hard, it is very tightly congealed; it can not, like snow, be easily melted. Snow, hardened by many years' duration, and by the succession of ages, is called "crystal," and this "He sends like morsels of bread." What means this? …

Exposition on Psalm 147 ↗

Jerome

He sends his crystal like morsels. As his loaves are broken and become morsels, so too this crystal is broken and turned into morsels. Crystal has this nature: it forms whenever waters are frozen — what we call ice. Between crystal and water, then, there is the same difference as between water and ice: for water is poured out, as it were, very broadly, whereas crystal is, as it were, compacted into itself, and reduced into one form. Whenever water freezes, it makes crystal. …

Homily 57, on Psalm 147 ↗