Srimad-Bhagavatam: Canto 9 - Chapter 1 - Verse 6
स एकदाष्टकाश्राद्धे इक्ष्वाकु: सुतमादिशत् ।मांसमानीयतां मेध्यं विकुक्षे गच्छ मा चिरम् ॥ ६ ॥
sa ekadāṣṭakā-śrāddheikṣvākuḥ sutam ādiśatmāṁsam ānīyatāṁ medhyaṁvikukṣe gaccha mā ciram
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.