Skandapurana 1.4.38.123

1.4.38.123

dānaṃ vānyaśca yatkiṃcidakṣayaṃ tadbhaviṣyati..
māghāsitacaturdaśyāṃ śivayoge ca putraka.. 40.123 ..

or a gift, or whatever else [is offered], that will become imperishable. / On the fourteenth day of the dark fortnight of Māgha, and during an auspicious conjunction with Śiva, O son,