Āśvalāyana(Aswalayana) is one of the Brahmavādī (Those who speak of Brahman, the Absolute Divine Self) sons of Sage Viśvāmitra (Viswamitra), as mentioned in Anuśāsanaparva(Anusasanaparva) of Mahābhārata (Mahabharata).

Mahābhārata (Kinjawadekar)(13.4.54)
Mahābhārata Vols. 1-43 (Siddhāntabāgīśa)(13.3.73)