SB 11.14.25

yathāgninā hema malaṁ jahāti
 dhmātaṁ punaḥ svaṁ bhajate ca rūpam
ātmā ca karmānuśayaṁ vidhūya
 mad-bhakti-yogena bhajaty atho mām
Synonyms: 
yathā — just as; agninā — by fire; hema — gold; malam — impurities; jahāti — gives up; dhmātam — smelted; punaḥ — again; svam — its own; bhajate — enters; ca — also; rūpam — form; ātmā — the spirit soul or consciousness; ca — also; karma — of fruitive activities; anuśayam — the resultant contamination; vidhūya — removing; mat-bhakti-yogena — by loving service to Me; bhajati — worships; atho — thus; mām — Me.
Translation: 
Just as gold, when smelted in fire, gives up its impurities and returns to its pure brilliant state, similarly, the spirit soul, absorbed in the fire of bhakti-yoga, is purified of all contamination caused by previous fruitive activities and returns to its original position of serving Me in the spiritual world.
Purport: 

According to Śrīla Viśvanātha Cakravartī Ṭhākura, this verse indicates that the devotee goes back home, back to Godhead, and there worships Lord Kṛṣṇa in his original spiritual body, which is compared to the original pure form of smelted gold. Gold alloyed with inferior metals cannot be purified by water and soap; similarly, the heart’s impurities cannot be removed by superficial processes. Only the fire of love of Godhead can cleanse one’s soul and send one back home, back to Godhead, to engage in eternal loving service to the Lord.