12. through—literally, "by the hand of," that is, by the agency of.
branches—literally, "ears"; so the olive branches are called, because as ears are full of grain, so the olive branches are full of olives.
golden oil—literally, "gold," that is, gold-like liquor.
out of themselves—Ordinances and ministers are channels of grace, not the grace itself. The supply comes not from a dead reservoir of oil, but through living olive trees (Ps 52:8; Ro 12:1) fed by God.