As a person puts on new garments, giving up old ones, the soul similarly accepts new material bodies, giving up the old and useless ones.
Change of body by the atomic individual soul is an accepted fact. Even the modern scientists who do not believe in the existence of the soul, but at the same time cannot explain the source of energy from the heart, have to accept continuous changes of body which appear from childhood to boyhood and from boyhood to youth and again from youth to old age. From old age, the change is transferred to another body. This has already been explained in a previous verse (2.13).
Transference of the atomic individual soul to another body is made possible by the grace of the Supersoul. The Supersoul fulfills the desire of the atomic soul as one friend fulfills the desire of another. The Vedas, like the Muṇḍaka Upaniṣad, as well as the Śvetāśvatara Upaniṣad, compare the soul and the Supersoul to two friendly birds sitting on the same tree. One of the birds (the individual atomic soul) is eating the fruit of the tree, and the other bird (Kṛṣṇa) is simply watching His friend. Of these two birds—although they are the same in quality—one is captivated by the fruits of the material tree, while the other is simply witnessing the activities of His friend. Kṛṣṇa is the witnessing bird, and Arjuna is the eating bird. Although they are friends, one is still the master and the other is the servant. Forgetfulness of this relationship by the atomic soul is the cause of one's changing his position from one tree to another, or from one body to another. The jīva soul is struggling very hard on the tree of the material body, but as soon as he agrees to accept the other bird as the supreme spiritual master—as Arjuna agreed to do by voluntary surrender unto Kṛṣṇa for instruction—the subordinate bird immediately becomes free from all lamentations. Both the Muṇḍaka Upaniṣad (3.1.2) and Śvetāśvatara Upaniṣad (4.7) confirm this:
samāne vṛkṣe puruṣo nimagno
'nīśayā śocati muhyamānaḥ
juṣṭaṁ yadā paśyaty anyam īśam
asya mahimānam iti vīta-śokaḥ
"Although the two birds are in the same tree, the eating bird is fully engrossed with anxiety and moroseness as the enjoyer of the fruits of the tree. But if in some way or other he turns his face to his friend who is the Lord and knows His glories—at once the suffering bird becomes free from all anxieties." Arjuna has now turned his face towards his eternal friend, Kṛṣṇa, and is understanding the Bhagavad-gītā from Him. And thus, hearing from Kṛṣṇa, he can understand the supreme glories of the Lord and be free from lamentation.
Arjuna is advised herewith by the Lord not to lament for the bodily change of his old grandfather and his teacher. He should rather be happy to kill their bodies in the righteous fight so that they may be cleansed at once of all reactions from various bodily activities. One who lays down his life on the sacrificial altar, or in the proper battlefield, is at once cleansed of bodily reactions and promoted to a higher status of life. So there was no cause for Arjuna's lamentation.
(Bhagavad-Gita--2:22--translation and purport).

Even if a person is fully addicted to all sorts of sinful acts, if he happens to be engaged in the loving transcendental service of the Lord under proper guidance, he is to be considered the most perfect holy man without a doubt. And thus any person, whatsoever and whosoever he or she may be—even the fallen woman, the less intelligent laborer, the dull mercantile man, or even a man lower than all these—can attain the highest perfection of life by going back home, back to Godhead, provided he or she takes shelter of the lotus feet of the Lord in all earnestness. This sincere earnestness is the only qualification that can lead one to the highest perfectional stage of life, and unless and until such real earnestness is aroused, there is a difference between cleanliness or uncleanliness, learning or nonlearning, in the material estimation. Fire is always fire, and thus if someone touches the fire, knowingly or unknowingly, the fire will act in its own way without discrimination. The principle is: harir harati pāpāni duṣṭa-cittair api smṛtaḥ. The all-powerful Lord can purify the devotee of all sinful reactions, just as the sun can sterilize all sorts of infections by its powerful rays. "Attraction for material enjoyment cannot act upon a pure devotee of the Lord." There are hundreds and thousands of aphorisms in the revealed scriptures. Ātmārāmāś ca munayaḥ: "Even the self-realized souls are also attracted by the transcendental loving service of the Lord." Kecit kevalayā bhaktyā vāsudeva-parāyaṇāḥ: (S.B.6:1:15) "Simply by hearing and chanting, one becomes a great devotee of Lord Vāsudeva." Na calati bhagavat-padāravindāl lavanimiṣārdham api sa vaiṣṇavāgryaḥ: "A person who does not move from the lotus feet of the Lord even for a moment or a second is to be considered the greatest of all Vaiṣṇavas." Bhagavat-pārṣadatāṁ prāpte mat-sevayā pratītaṁ te: "The pure devotees are convinced of attaining the association of the Personality of Godhead, and thus they are always engaged in the transcendental loving service of the Lord." Therefore in all continents, in all planets, in all universes, devotional service to the Lord, or bhakti-yoga, is current, and that is the statement of the Śrīmad-Bhāgavatam and allied scriptures. Everywhere means in every part of the creation of the Lord. The Lord can be served by all the senses, or even simply by the mind. The South Indian brāhmaṇa who served the Lord simply on the strength of his mind also factually realized the Lord. Success is guaranteed for a devotee who fully engages any one of his senses in the mode of devotional service. The Lord can be served by any ingredient, even the most common commodity—a flower, a leaf, a fruit or a little water, which are available in any part of the universe and without cost—and thus the Lord is served universally by the universal entities. He can be served simply by hearing, He can be served simply by chanting or reading about His activities, He can be served simply by adoring Him and accepting Him.
(Srimad Bhagavatam--2:9:36--purport).