Udyoga Parva, Adhyāya 101: Bhogavatī-varṇana, Nāga-vaṃśa-kathana, and Sumukha-vivāha-prastāva
आसां तु पयसा मिश्र पयो निर्मथ्य सागरे | मन्थानं मन्दरं कृत्वा देवैरसुरसंहितै:
āsāṃ tu payasā miśraṃ payo nirmathya sāgare | manthānaṃ mandaraṃ kṛtvā devair asurasaṃhitaiḥ ||
नारद उवाच—आसां धेनूनां पयसा मिश्रं क्षीरं सागरे निर्मथ्य, मन्दरं मन्थानं कृत्वा देवैरसुरसंहितैः; तस्मान्मन्थनाद्वारुणी श्रीरमृतं च प्रादुरभवत्, ततश्चोच्चैःश्रवा अश्वराजः कौस्तुभमणिरत्नं च।
नारद उवाच
The verse suggests that even opposing groups can unite for a common goal, but the benefits gained (wealth, power, immortality) must be handled under dharma; otherwise, they become seeds of further rivalry and moral decline.
Nārada recounts the mythic churning of the Ocean of Milk: the devas and asuras cooperate, using Mandara as the churning rod, and from the churning emerge Vāruṇī, Lakṣmī, amṛta, the horse Uccaiḥśravā, and the jewel Kaustubha.