Chapter IV Sloka 38

n ih }anen s†z< pivÇimh iv*te, 
tTSvy< yaegs<isÏ> kalenaTmin ivNdit.

na hi jñ˜nena sad®þaÕ 
pavitramiha vidyate | 
tatsvayaÕ yogasaÕsiddha× 
k˜len˜tmani vindati ( 4|38)||

Verily, there is no purifier in this would like knowledge. He who is perfected in Yoga finds it in the Self in time.
Commentary: There exists no purifier equal to knowledge of the Self. He who has attained perfection by the constant practice of Karma Yoga and Dhyana Yoga (the Yoga of Meditation) will, after a time, find the knowledge of the Self in himself.

Kalena: Chinmayananda explains that perfection as a result of practising all the twelve different yagnas sincerely and devotedly, will manifest "in good time" or "ere-long" achirena as mentioned in the next slokam.