You have asked what is Kah, who is endued with change, and who is unendued therewith. I answer, Kah is Soul. That which is endued with change is Nature. He who is not endued therewith is Soul.
कस्तपा अतपाः प्रोक्तः कोऽसौ पुरुष उच्यते। तपास्तु प्रकृति प्राहुरतपा निष्कलः स्मृतः॥