Rama is known as embodiment of Dharma. He followed his father's words and went to exile for 14 years. When Rama was ordered to leave the city to leave to forest, his mother Kaikeyi and his brother Lakshmana try to console him to leave Ayodhya. For this, Lord Rama answers taking many examples from ancient history where following father's commands is glorified and called as dharma. While he was giving examples, he names a sage Kandu who killed a cow according to his father's words.
Ṝṣiṇā ca pitur vākyam kurvatā vrata cāriṇā |
gaur hatā jānatā dharmam kaṇḍunā api vipaścitā || 2-21-30 (Sarga 21 Ayodhya Kanda)
"A sage called Kandu, who knew righteousness, who performed religious vows and who was a learned man, killed even a cow, acting as per his father's words"
Vishnu Purana (Amsha 1 adhyaya 14) gives the story of sage Kandu about his penance to Lord Vishnu. This penance was disturbed by Indra by sending an apasara Pramlocā. Brahma Purana purvabhaga (first part) has a continuation to this story where he goes to Purushottama kshetra and also does a eulogy to Vishnu for expiation of sins committed. But there was no mention of him killing cow following father's words.
What is the story where he killed a cow following his father's orders?