Nābhāga’s father said: All the descendants of Aṅgirā are now going to perform a great sacrifice, but although they are very intelligent, on every sixth day they will be bewildered in performing sacrifice and will make mistakes in their daily duties.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
इमे अङ्गिरसः सत्रमासतेऽद्य सुमेधसः । षष्ठं षष्ठमुपेत्याहः कवे मुह्यन्ति कर्मणि
ime aṅgirasaḥ satramāsate'dya sumedhasaḥ | ṣaṣṭhaṃ ṣaṣṭhamupetyāhaḥ kave muhyanti karmaṇi
SB 9.4.3