Bg 6.45

prayatnad yatamanas tu
yogi samsuddha-kilbisah
aneka-janma-samsiddhas
tato yati param gatim

Word for word: 
prayatnat — by rigid practice; yatamanah — endeavoring; tu — and; yogi — such a transcendentalist; samsuddha — washed off; kilbisah — all of whose sins; aneka — after many, many; janma — births; samsiddhah — having achieved perfection; tatah — thereafter; yati — attains; param — the highest; gatim — destination.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
And when the yogi engages himself with sincere endeavor in making further progress, being washed of all contaminations, then ultimately, achieving perfection after many, many births of practice, he attains the supreme goal.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
A person born in a particularly righteous, aristocratic or sacred family becomes conscious of his favorable condition for executing yoga practice. With determination, therefore, he begins his unfinished task, and thus he completely cleanses himself of all material contaminations. When he is finally free from all contaminations, he attains the supreme perfection – Krishna consciousness. Krishna consciousness is the perfect stage of being freed of all contaminations. This is confirmed in the Bhagavad-gita (7.28):

yesam tv anta-gatam papam
jananam punya-karmanam
te dvandva-moha-nirmukta
bhajante mam drdha-vratah

“After many, many births of executing pious activities, when one is completely freed from all contaminations, and from all illusory dualities, one becomes engaged in the transcendental loving service of the Lord.”