Hi NP,
Being numerous means having abundant descendants as God promised when He introduced His covenant with Abraham:
And he brought him forth abroad, and said, Look now toward heaven, and tell the stars, if thou be able to number them: and he said unto him, So shall thy seed be. (Gen 15:5)
The Hebrew/ Christian Scripture, overall, is a series of covenants God makes with with His people.
In short (very short), through these covenants, God makes oaths "I will be their God. They shall be my people." In these series of covenants, God promises to provide for his people, forgive their sins, make them abundant and numerous, make them a mighty people, deliver them from enemies, which are ultimately sin and resulting death. The people in turn make oaths to worship God, obey Him, make offerings, repent.
Approached with a sincere eye to spirituality and not simply custom, Yom Kippur is a powerful and profound religious observation, potentially infusing this namesake poem with a strong foundation of meaning. Meaning, which, I think, Shultz, built on beautifully.
Sometimes a poem with the theme of religious observation fails in that, once it mentions it custom, it flat-lines on the name-dropped short-hand the and the corresponding cliches. I think Schultz avoided those short-hand failures and spoke to the heart of Yom Kippur-- of what is a man guilty and for what can a man be forgiven by his God?
I'd be thrilled if any one of the pro- Yom Kippur critiques might influence somebody to read this week's poem more positively.