Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 25
Sanskrit:
राक्षसं भावमापन्न: पादे कल्माषतां गत: ।व्यवायकाले ददृशे वनौकोदम्पती द्विजौ ॥ २५ ॥
ITRANS:
rākṣasaṁ bhāvam āpannaḥpāde kalmāṣatāṁ gataḥvyavāya-kāle dadṛśevanauko-dampatī dvijau
Translation:
Saudāsa thus acquired the propensity of a man-eater and received on his leg a black spot, for which he was known as Kalmāṣapāda. Once King Kalmāṣapāda saw a brāhmaṇa couple engaged in sexual intercourse in the forest.