Srimad Bhagavatam Canto 09, Chapter 06, Text 06

SB 9.6.6

sa ekadastaka-sraddhe
 iksvakuh sutam adisat
mamsam aniyatam medhyam
 vikukse gaccha ma ciram
 
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
During the months of January, February and March, oblations offered to the forefathers are called astaka-sraddha. The sraddha ceremony is held during the dark fortnight of the month. When Maharaja Iksvaku was performing his oblations in this ceremony, he ordered his son Vikuksi to go immediately to the forest to bring some pure flesh.
Srimad Bhagavatam Canto 09, Chapter 06, Text 05
Srimad Bhagavatam Canto 09, Chapter 06, Text 07