Skandapurana 16.118.31

16.118.31

nīlaraktena vastreṇa yatkarma kurute dvijaḥ ..
snānaṃ dānaṃ japo homaḥ svādhyāyaḥ pitṛtarpaṇam ..
vṛthā tasya mahāyajñā nīlasūtrasya dhāraṇāt .. 31 ..

Whatever rite a twice-born performs wearing a garment dyed blue— / ritual ablution, gifts, recitation of mantras, oblations, study of the Veda, offerings to the ancestors— / his great sacrifices are in vain, because of wearing indigo thread. // 31