And how, Ananda, do disciples conduct themselves towards a teacher with friendliness, not with hostility? As to this, Ananda, the teacher, compassionate, teaches dhamma to disciples, seeking their welfare, out of compassion, saying: 'This is for your welfare, this is for your happiness.' And his disciples listen, lend ear, prepare their minds for profound knowledge and, not turning aside, they do not move away from the techer's instruction. Even so, Ananda, do a teacher's disciples conduct themselves towards him with friendliness, not with hostility. Wherefore, Ananda, conduct yourselves towards me with friendliness, not with hostility; for a long Time that will be for your welfare and happiness. And I, Ananda, will not proceed with you as does a potter with an unbaked (vessel), not fully dry. I will speak, Ananda, constantly reproving, constantly cleansing. That which is the pith will stand fast.
Ms. Horner has this footnote:
"The potter gently takes these vessels in both hands, saying: 'Do not break'; but I will not proceed with you as the potter proceeds. I do not see the full force of this simile; therefore my translation must remain very tentative. But I believe it means that whereas the potter gives, and can give, his vessels one chance only, the Teacher is undefeated by any initial failure there may be, and proceeds undeterred with the expectation of final success on the part of his pupil."
I think this is a partial misunderstanding. The Teacher is not just "undefeated by any initial failure" he has had no failure, his instructions have not been incorrectly taught, and as to how they are received, he is totally indifferent. Though the Potter (Bhaggava) may be upset that "his" work has been destroyed if a half baked crock gets bent out of shape, The Bhaggava has no thought of "My Student". Furthermore, it is in fact a vital lesson for a student that he is not going to be "handled" by the teacher but must fend for himself (be a light unto himself); and further to the furthermore is the fact that the student will know when he is being "handled" and will come to depend on that and That would be an incorrect instruction to be giving. This is the meaning as I hear it.
An interesting and very different understanding of this line is found in the H.E. Musson (aka Bhikkhu Nanavira) translation from the Italian of Evola's "The Doctrine of Awakening" (Inner Traditions, Vermont, pp 18):
"I will not force you, as the potter his raw clay. By reproving I will instruct, and by urging you. He who is sound will endure.
 PED: Bhagga1 broken ... applied metaphorically at Dh 154, expld DhA III.128 (artificially) by "avasesa-kilesa-phāsukā bhaggā";...and bhagga-rāga, -dosa etc. (in def. of Bhagavā) at Nd1 142=Nd2 466 B, quoted at Vism 211.
Bhagga2 [fr. bhaga; cp. Sk. and P. bhāgya] fortune, good luck, welfare, happiness
Bhaggava [cp. Sk. *bhārgava, a der. fr. bhr.gu, and bhargah., of same root as Lat. fulgur lightning; Gr. flo/c light; Ger. blitzen, blank; Ags. blanca white horse, all of the idea of "shining, bright, radiant." - How the meaning "potter" is connected with this meaning, is still a problem, perhaps we have to take the word merely as an Epithet at the one passage where it occurs, which happens to be in the Kumbhakāra-jātaka, v. 6, 7. i. e. the "Jātaka of the potter"] potter (?) J III.381, 382, in voc. bhaggava (m.) and bhaggavī (f.). The terms are not expld in C., evidently because somewhat obscure. According to Kern, Toev. s. v. the Sk. form in this meaning occurs at MBh. I.190, 47; Saddhp. 191 sq., MVastu III.347.
 Rubaiyat of Omar Khayyam
Listen again! One Evening at the Close
Of Ramazan, ere the better Moon arose,
In that old Potter's Shop I stood alone
With the clay Population round in Rows.
And, strange to tell, among that Earthen Lot
Some could articulate, while others not:
And suddenly one more impatient cried
"Who is the Potter, pray, and who the Pot?"