That saintly Dadhyañca, who is also known as Dadhīci, personally assimilated the spiritual science and then delivered it to the Aśvinī-kumāras. It is said that Dadhyañca gave them mantras through the head of a horse. Therefore the mantras are called Aśvaśira. After obtaining the mantras of spiritual science from Dadhīci, the Aśvinī-kumāras became jīvan-mukta, liberated even in this life.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
स वा अधिगतो दध्यङ्ङश्विभ्यां ब्रह्म निष्कलम् । यद्वा अश्वशिरो नाम तयोरमरतां व्यधात्
sa vā adhigato dadhyaṅṅaśvibhyāṃ brahma niṣkalam | yadvā aśvaśiro nāma tayoramaratāṃ vyadhāt
SB 6.9.52