Bhashya
दध्नः सोम्य मथ्यमानम्य योऽणिमा अणुभावः स ऊर्ध्वःसमुदीषति संभूयोर्ध्वं नवनीतभावेन गच्छति, तत्सर्पिर्भवति ॥
In plain words
When curd is being churned, my dear, that subtle, microscopic essence rises upward, gathers together at the top in the form of fresh butter, and turns into butter.
Close to the Sanskrit
Of curd, my dear, being churned, whichever is the subtlety, the atomic state, that rising upward, coming together upward in the state of fresh butter, goes, that becomes butter.