This is a Shruti given out by the Rishis Atharva and Angira, the best of all the Srutis; people who wish well should always follow this without any scruple.
अथर्वाङ्गिरसी ह्येषा श्रुतीनामुत्तमा श्रुतिः। अविचार्यैव कार्येषा श्रेयस्कामैनरैः सदा॥