en_tn_condensed/mat/13/32.md

This seed is indeed the smallest of all seeds

Mustard seeds were the smallest seeds known to the original hearers. (See: rc://en/ta/man/translate/figs-explicit)

But when it has grown

"But when the plant has grown"

it is greater than

"it is larger than"

becomes a tree

A mustard plant can grow about 2 to 4 meters tall.

birds of the sky

"birds"