Charles H. Spurgeon on Psalms 133:2

Down upon the beard, even Aaron's beard: that went down to the skirts of his garments. Not the extremity of them, as our version inclines to; for not so great a quantity of oil was poured upon him; nor would it have been decent to have his clothes thus greased from top to bottom; but the upper part of his garment, the top of his coat, on which the beard lay, as Zarchi; the neck or collar of it, as Kimchi and Ben Melech; the hole in which the head went through when it was put on, about which there was a band, that it might not be rent: Ex 28:32 39:23; where the Septuagint use the same word as here. —John Gill.

Verses 2-3. In this prayer and song of the unity of the church, it is note worthy how, commencing with the fundamental idea of "brethren", we rise to the realization of the Elder Brother, who is our common anointed High Priest. It is the bond of his priesthood which joins us together as brethren. It is the common anointing which flows down even to the skirts of the garment of our High Priest which marks our being brethren. Whether we dwell north or south, meeting in Zion, and sharing in the blessings of that eternal Priesthood of Christ, we form in reality, and before our Father, but one family —"the whole family in earth and heaven." Our real bond of union consists in the "flowing down", the "running down", or "descending" of the common blessing, which marks the steps in this Psalm of Degrees (Ps 133:2-3). And if "the dew of Hermon" has descended upon "the mountains of Zion", long after the sun has risen shall gladsome fruit appear —in some twenty, in some thirty, and in some a hundred fold. —Alfred Edersheim