Agni is equally the sacred fire as well as the deity of that hearth who transmits oblations to the other deities. Hence, this mantra is recited though invoking the deity Agni in the form of fire as witness into the vow. Agne vratapate vrataṃ cariṣyāmi (Vājasaneyī-Saṃhitā from the Śukla [White] https://cypriotdirectory.com/listings13318580/baglamukhi-fundamentals-explained