Psalms 133

1 A Song of Ascents; 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 It is like the precious oil upon the head, coming down upon the beard; even Aaron's beard, that cometh down upon the collar 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 Like the dew of Hermon, that cometh down upon the mountains of Zion; for there the LORD commanded the blessing, even life for ever.

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.