During the months of January, February and March, oblations offered to the forefathers are called aṣṭakā-śrāddha. The śrāddha ceremony is held during the dark fortnight of the month. When Mahārāja Ikṣvāku was performing his oblations in this ceremony, he ordered his son Vikukṣi to go immediately to the forest to bring some pure flesh.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
स एकदाष्टकाश्राद्धे इक्ष्वाकुः सुतमादिशत् । मांसमानीयतां मेध्यं विकुक्षे गच्छ मा चिरम्
sa ekadāṣṭakāśrāddhe ikṣvākuḥ sutamādiśat | māṃsamānīyatāṃ medhyaṃ vikukṣe gaccha mā ciram
SB 9.6.6