Ramayana
वरः खलु मयैतस्मै दत्तस्त्रिदशपुङ्गव । स त्वया नानृतः कार्यो यन्मया व्याहृतं वचः ॥ 7-22-40 ॥
"For a boon was indeed granted by me to him, O bull among the gods; that word which was uttered by me must not be made false by you."
english translation