Manava Dharmashastra 4.58

4.58

agnyagāre gavāṃ goṣṭhe brāhmaṇānāṃ ca saṃnidhau
svādhyāye bhojane caiva dakṣinaṃ pāṇim uddharet //

Let him keep his right arm uncovered in a place where a sacred fire is kept, in a cow-pen, in the presence of Brahmanas, during the private recitation of the Veda, and at meals.