Paithinasidharmasutra 5.14: Vīramitrodaya · Nirṇayasindhu · Hiraṇyakeśiśrautasūtra

5.14

ādyendāv eva kartavyāḥ pretapiṇḍodakakriyāḥ | dviraindave tu kurvāṇaḥ punaḥ śāvaṃ samaśnute

The rites of the ball of rice and water for the ghost must be performed only in the first [intercalary/lunar] month; / but one who performs them in an intercalary month incurs corpse-impurity once again.

The rice-balls and water for the departed are to be offered in the first lunar month; one who does them in the second incurs death-impurity again.