One verse

Srimad Bhagavatam 10.1.8

10.1.8

रोहिण्यास्तनय: प्रोक्तो राम: सङ्कर्षणस्त्वया । देवक्या गर्भसम्बन्ध: कुतो देहान्तरं विना ॥ ८ ॥

rohiṇyās tanayaḥ prokto rāmaḥ saṅkarṣaṇas tvayā devakyā garbha-sambandhaḥ kuto dehāntaraṁ vinā

rohiṇyāḥ
of Rohiṇīdevī, the mother of Baladeva
tanayaḥ
the son
proktaḥ
is well known
rāmaḥ
Balarāma
saṅkarṣaṇaḥ
Balarāma is none other than Saṅkarṣaṇa, the first Deity in the quadruple group (Saṅkarṣaṇa, Aniruddha, Pradyumna and Vāsudeva)
tvayā
by you (it is so said)
devakyāḥ
of Devakī, the mother of Kṛṣṇa
garbha-sambandhaḥ
connected with the womb
kutaḥ
how
deha-antaram
transferring bodies
vinā
without

My dear Śukadeva Gosvāmī, you have already explained that Saṅkarṣaṇa, who belongs to the second quadruple, appeared as the son of Rohiṇī named Balarāma. If Balarāma was not transferred from one body to another, how is it possible that He was first in the womb of Devakī and then in the womb of Rohiṇī? Kindly explain this to me.