This was said by the Buddha, the Perfected One: that is what I heard. Vuttañhetaṁ bhagavatā vuttamarahatāti me sutaṁ:

“Taking into account interior factors, mendicants, I do not see a single one that is so very helpful as rational application of mind for a trainee mendicant who hasn’t achieved their heart’s desire, but lives aspiring to the supreme sanctuary from the yoke. “Sekhassa, bhikkhave, bhikkhuno appattamānasassa anuttaraṁ yogakkhemaṁ patthayamānassa viharato ajjhattikaṁ aṅganti karitvā nāññaṁ ekaṅgampi samanupassāmi yaṁ evaṁ bahūpakāraṁ yathayidaṁ, bhikkhave, yoniso manasikāro. A mendicant rationally applying the mind gives up the unskillful and develops the skillful.” Yoniso, bhikkhave, bhikkhu manasi karonto akusalaṁ pajahati, kusalaṁ bhāvetī”ti.

The Buddha spoke this matter. Etamatthaṁ bhagavā avoca. On this it is said: Tatthetaṁ iti vuccati:

“There is nothing so helpful “Yonisomanasikāro, for a trainee mendicant dhammo sekhassa bhikkhuno; aspiring for the ultimate goal Natthañño evaṁ bahukāro, as rational application of mind. uttamatthassa pattiyā; Striving rationally, a mendicant Yoniso padahaṁ bhikkhu, attains the end of suffering.” khayaṁ dukkhassa pāpuṇe”ti.

This too is a matter that was spoken by the Blessed One: that is what I heard. Ayampi attho vutto bhagavatā, iti me sutanti.

Chaṭṭhaṁ.