It’s Hymn of Lord Rudra. It can be found both in Rig Veda as well as Yajur Veda. It mostly consists of verses taken from the Sri Rudram chant.
One can sing and chant during the time of Puja. It has several benefits. Anyone singing it, can not be affected by any Ghosts, Pret, chudel, Pisach etc. Not only that the person, singing it for Lord Shiva will be untouchable for demons, evil and wicked People. Tantra Vidhya effect will not harm him also. No any Tantra Vidhya will effect such personality. No snake or cobra or any bite will effect on him.
But one should chant it with pious and pure heart during the time of Puja and if possible, it should be total suktam on tongue.
namo bhavāya cha rudrāya cha
namaḥ śarvāya cha paśupataye cha
namo nīlagrīvāya cha śitikaṇṭhāya cha
namaḥ kapardine cha vyuptakeshāya cha
namaḥ sahasrākṣāya cha śatadhanvane cha
namo girīśāya cha śipiviṣṭāya cha
Prostration to the one who is the most dear (pleasant), to the one who is the most dreaded terroriser (frightening).
Prostration to the one who kills living beings with arrows, to the Lord (benefactor) of all living beings.
Prostration to the blue-necked one (disfigured (discoloured) naturally), to the one with whitened throat (throat smeared with Bhasma (ash); disfigured (discoloured) artificially).
Prostration to the wearer of matted tangled locks of hair, to him of shaven beard.
Prostration to him of a thousand eyes (view from one point to everywhere), to him who has the capability of hundred bowmen (view from everywhere to one point - concentration of the view from all directions).
Prostration to the Lord of mountains (conjoint into a mass), and to him who is all pervasive (disjoint and diffusing everywhere).