Ramayana
ततो ऽश्वमेधः सुमहान्महेन्द्रस्य महात्मनः । ववृधे ब्रह्महत्ययाः पावनार्थं नरेश्वर ॥ 7-86-9 ॥
Then, O lord of men, that exceedingly great horse-sacrifice of the high-souled Mahendra grew to its full measure, for the purpose of cleansing the sin of brahmin-slaying.
english translation