In plain words
The poet, to the Lord of Araṅgam: O you who dwell in the great city of Araṅgam! Even brahmins by birth, who have learned firmly by heart the six unique limbs [of the Veda] and the four incomparable Vedas and are foremost among your people, if they revile your servants, then in the space of a finger-snap, right there, they themselves become outcastes.