One should never take his mcals without cating some sesame. One should never teach (the Vedas or any scriptures) at a time when he is impure. Nor should onc study while is impure.
तिलसृष्टं न चाश्नीयात् तथास्यायुर्न रिष्यते॥ नाध्यापयेत् तथोच्छिष्टो नाधीयीत कदाचन।