“As you yourself wish to become a speaker, and cannot learn this with greater ease from anyone else, just attend, dear lad, to all that I shall say, copy me in everything, and always keep, I beg you, the rules which I shall bid you to follow. ‘In fact, you may press on at once; you need not feel any hesitation or dismay because you have not gone through all the rites of initiation preliminary to Rhetoric, through which the usual course of elementary instruction guides the steps of the senseless and silly at the cost of great weariness. You will not require them at all. No, go straight in, as the proverb says, with unwashen feet,

The saying in full was ἀνίπτοις ποσὶν ἀναβαίνων ἐπὶ τὸ στέγος (going up to the roof with unwashed feet), and so can hardly contain any reference to ceremonial purification. Perhaps going up on the roof was tantamount to going to bed, Cf. Song of Solomon, 5, 3.

and you will not fare any the worse for that, even if you are quite in the prevailing fashion and do not know how to write. Orators are beyond all that!