Mudgalapurana 3.21.20

3.21.20

khaṃ. 3 a. 21 pāna 43) pūrṇimādyā amāntā yāstithayaḥ kṛṣṇapakṣake |
caturdaśīṃ varjayitvā praśastāḥ śrāddhakarmaṇi ||

[khaṇḍa 3, adhyāya 21, page 43] The lunar days in the dark fortnight from the full moon to the new moon, / with the exception of the fourteenth, are praised in the rite of śrāddha.