Inclusio

Same way.

This is called an inclusio.

Inclusio.

where the author places the same word, the same theme, the same phrase at the beginning and at the end to kind of frame everything that falls in between in kind of an all-encompassing way.

So in other words, from verse 3 to verse 10, all of the Beatitudes are meant to describe the qualities of the citizens of the kingdom of God.