Sutra 4.2.4

4. That (is united) with the ruler, on account of the going to it, and so on.

As from the statements that speech becomes united with mind and mind with breath it follows that speech and mind are united with mind and breath only; so we conclude from the subsequent clause 'breath with fire' that breath becomes united with fire only.—Against this primā facie view the Sūtra declares 'that breath becomes united with the ruler of the organs, i.e. the individual soul, on account of the going to it, and so on.' That breath goes to the individual soul, the following text declares, 'At the time of death all the prāṇas go to the Self of a man about to expire ' (Bṛ. Up. IV, 3, 38), Similarly Scripture mentions the departure of prāṇa together with the soul, 'after him thus departing the prawa departs'; and again its staying together with the soul, 'What is that by whose departure I shall depart, and by whose staying I shall stay?' (Pr. Up. VI, 3). We therefore conclude that the text 'breath with fire' means that breath joined with the individual soul becomes united with fire. Analogously we may say in ordinary life that the Yamuna is flowing towards the sea, while in reality it is the Yamuna joined with the Gangā which flows on.—Here terminates the adhikaraṇa of 'the ruler.'