On account of those remains of a Shudra's food in his stomach, he falls away from the position of a Brahmana. Such a Brahmana becomes surely a Shudra.
तेन शूद्रानशेषेण ब्रह्मस्थानादपाकृतः। ब्राह्मणः शूद्रतामेति नास्ति तत्र विचारणा॥