Vayu Purana 1.15.9

Vāyupurāṇa 1.15.9

oṃprāṇānāṃ granthirasyātmā rudro hyātmā viśāntakaḥ.
sa rudro hyātmanaḥ prāṇā evamāpyāyayet svayam .. 15.8 ..