SB 10.22.28

śrī-śuka uvāca
ity ādiṣṭā bhagavatā
 labdha-kāmāḥ kumārikāḥ
dhyāyantyas tat-padāmbhojam
 kṛcchrān nirviviśur vrajam
śrī-śukaḥ uvāca — Śrī Śukadeva Gosvāmī said; iti — thus; ādiṣṭāḥ — instructed; bhagavatā — by the Supreme Personality of Godhead; labdha — having obtained; kāmāḥ — their desire; kumārikāḥ — the young girls; dhyāyantyaḥ — meditating; tat — His; pada-ambhojam — upon the lotus feet; kṛcchrāt — with difficulty; nirviviśuḥ — they returned; vrajam — to the cowherd village.
Śukadeva Gosvāmī said: Thus instructed by the Supreme Personality of Godhead, the young girls, their desire now fulfilled, could bring themselves only with great difficulty to return to the village of Vraja, meditating all the while upon His lotus feet.

The gopīs’ desire was fulfilled because Lord Kṛṣṇa had agreed to act as their husband. A young girl can never spend the night with any man except her husband, and thus when Kṛṣṇa agreed to engage the girls in the nocturnal rāsa dance during the coming autumn season, in effect He was agreeing to reciprocate their love for Him in the role of a husband.