Ramayana
ततो ऽग्निसाक्षिकं सख्यं कृतवांस्तत्र रावणः । निवातकवचैः सार्धं प्रीतिमानभवत्तदा ॥ 7-23-14 ॥
Then Ravana made a friendship there with fire as witness, and at that time he became filled with affection toward the Nivatakavachas.
english translation