Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 25
गोगोपीनां मातृतास्मिन्नासीत्स्नेहर्धिकां विना ।पुरोवदास्वपि हरेस्तोकता मायया विना ॥ २५ ॥
go-gopīnāṁ mātṛtāsminnāsīt snehardhikāṁ vināpurovad āsv api harestokatā māyayā vinā
Previously, from the very beginning, the gopīs had motherly affection for Kṛṣṇa. Indeed, their affection for Kṛṣṇa exceeded even their affection for their own sons. In displaying their affection, they had thus distinguished between Kṛṣṇa and their sons, but now that distinction disappeared.
The distinction between one’s own son and another’s son is not unnatural. Many elderly women have motherly affection for the sons of others. They observe distinctions, however, between those other sons and their own. But now the elderly gopīs could not distinguish between their own sons and Kṛṣṇa, for since their own sons had been taken by Brahmā, Kṛṣṇa had expanded as their sons. Therefore, their extra affection for their sons, who were now Kṛṣṇa Himself, was due to bewilderment resembling that of Brahmā. Previously, the mothers of Śrīdāmā, Sudāmā, Subala and Kṛṣṇa’s other friends did not have the same affection for one another’s sons, but now the gopīs treated all the boys as their own. Śukadeva Gosvāmī, therefore, wanted to explain this increment of affection in terms of Kṛṣṇa’s bewilderment of Brahmā, the gopīs, the cows and everyone else.