I have heard that on one occasion Ven. Ananda was staying in Kosambi, at Ghosita's Park. Then the Brahman Unnabha went to where Ven. Ananda was staying and on arrival greeted him courteously. After an exchange of friendly greetings & courtesies, he sat to one side. As he was sitting there, he said to Ven. Ananda: "Master Ananda, what is the aim of this holy life lived under Gotama the contemplative?"
"Brahman, the holy life is lived under the Blessed One with the aim of abandoning desire."
"Is there a path, is there a practice, for the abandoning of that desire?"
"Yes, there is a path, there is a practice, for the abandoning of that desire."
"What is the path, the practice, for the abandoning of that desire?"
"Brahman, there is the case where a monk develops the base of power endowed with concentration founded on desire & the fabrications of exertion. He develops the base of power endowed with concentration founded on persistence... concentration founded on intent... concentration founded on discrimination & the fabrications of exertion. This, Brahman, is the path, this is the practice for the abandoning of that desire."
"If that's so, Master Ananda, then it's an endless path, and not one with an end, for it's impossible that one could abandon desire by means of desire."
"In that case, brahman, let me question you on this matter. Answer as you see fit. What do you think: Didn't you first have desire, thinking, 'I'll go to the park,' and then when you reached the park, wasn't that particular desire allayed?"
"Yes, sir."
"Didn't you first have persistence, thinking, 'I'll go to the park,' and then when you reached the park, wasn't that particular persistence allayed?"
"Yes, sir."
"Didn't you first have the intent, thinking, 'I'll go to the park,' and then when you reached the park, wasn't that particular intent allayed?"
"Yes, sir."
"Didn't you first have [an act of] discrimination, thinking, 'I'll go to the park,' and then when you reached the park, wasn't that particular act of discrimination allayed?"
"Yes, sir."
"So it is with an arahant whose mental effluents are ended, who has reached fulfillment, done the task, laid down the burden, attained the true goal, totally destroyed the fetter of becoming, and who is released through right gnosis. Whatever desire he first had for the attainment of arahantship, on attaining arahantship that particular desire is allayed. Whatever persistence he first had for the attainment of arahantship, on attaining arahantship that particular persistence is allayed. Whatever intent he first had for the attainment of arahantship, on attaining arahantship that particular intent is allayed. Whatever discrimination he first had for the attainment of arahantship, on attaining arahantship that particular discrimination is allayed. So what do you think, brahman? Is this an endless path, or one with an end?"
"You're right, Master Ananda. This is a path with an end, and not an endless one. Magnificent, Master Ananda! Magnificent! Just as if he were to place upright what was overturned, to reveal what was hidden, to show the way to one who was lost, or to carry a lamp into the dark so that those with eyes could see forms, in the same way has Master Ananda — through many lines of reasoning — made the Dhamma clear. I go to Master Gotama for refuge, to the Dhamma, and to the Sangha of monks. May Master Ananda remember me as a lay follower who has gone for refuge, from this day forward, for life."