Psalms 133

1 A Song of degrees. Of David. Behold, how good and how pleasant it is for brethren to dwell together in unity!

It is very good and very pleasant for God’s people to gather together harmoniously.

2 Like the precious oil upon the head, that ran down upon the beard, upon Aaron's beard, that ran down to the hem of his garments;

It is [as delightful as] the precious/expensive ([olive] oil/perfume) that runs down from [the Supreme Priest] Aaron’s head onto his beard [when he is anointed] and runs down onto the collar of his robes.

3 As the dew of Hermon that descendeth on the mountains of Zion; for there hath Jehovah commanded the blessing, life for evermore.

Gathering together harmoniously [is as delightful] as the dew [that falls] on Hermon [Mountain] and the dew that falls on the hills near Zion [Hill]. Yahweh has promised to bless [his people there in Jerusalem] [by giving them] everlasting (OR, a long-lasting) life.