Bg 8.15

mam upetya punar janma
duhkhalayam asasvatam
napnuvanti mahatmanah
samsiddhim paramam gatah

Word for word: 
mam — Me; upetya — achieving; punah — again; janma — birth; duhkha-alayam — place of miseries; asasvatam — temporary; na — never; apnuvanti — attain; maha-atmanah — the great souls; samsiddhim — perfection; paramam — ultimate; gatah — having achieved.

Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
After attaining Me, the great souls, who are yogis in devotion, never return to this temporary world, which is full of miseries, because they have attained the highest perfection.

Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Since this temporary material world is full of the miseries of birth, old age, disease and death, naturally he who achieves the highest perfection and attains the supreme planet, Krishnaloka, Goloka Vrndavana, does not wish to return. The supreme planet is described in Vedic literature as avyakta and aksara and parama gati; in other words, that planet is beyond our material vision, and it is inexplicable, but it is the highest goal, the destination for the mahatmas (great souls). The mahatmas receive transcendental messages from the realized devotees and thus gradually develop devotional service in Krishna consciousness and become so absorbed in transcendental service that they no longer desire elevation to any of the material planets, nor do they even want to be transferred to any spiritual planet. They only want Krishna and Krishna’s association, and nothing else. That is the highest perfection of life. This verse specifically mentions the personalist devotees of the Supreme Lord, Krishna. These devotees in Krishna consciousness achieve the highest perfection of life. In other words, they are the supreme souls.