Ramayana
वरप्रदानाद्बलवान्न खल्वन्येन हेतुना । तत्तु सत्यवचः कार्यं यदुक्तं पद्मयोनिना ॥ 7-27-8 ॥
"It is by the granting of a boon that he is strong, and by no other cause; and that true word which was spoken by Brahma, the lotus-born, must be made to hold good."
english translation