Śatapatha Brāhmaṇa ("of a hundred paths") 13.8.1.4

13.8.1.4

śaradi kuryāt svadhā vai śaratsvadho vai pitṝṇāmannaṃ tadenamanne svadhāyāṃ dadhāti māghe vā mā no'gham bhūditi nidāghe vā ni no'ghaṃ dhīyātā iti

Let him make it in autumn, for the autumn is the Svadhâ, and the Svadhâ is the food of the Fathers: he thus places him along with food, the Svadhâ;--or in (the month of) Mâgha, thinking, 'Lest (mâ) sin (agha) be in us;'--or in summer (nidâgha), thinking, 'May thereby be removed (nidhâ) our sin (agha)!'