He was Abu Khaithama Zuhair Ibn Harb Ibn Shadaad An-Nasaa’ee.  He was a great Haafidh, reliable in narration and firm in memory. He narrated hadeeth from many scholars, the likes of Sufyaan Ibn 'Uyainah, Hushaim Ibn Basheer, Yahyaa Ibn Sa'eed Al-Qattaan, 'Abd-ur-Rahmaan Ibn Mahdee and Wakee'.
Similarly, many scholars narrated from him, such as Al-Bukhaaree and Muslim, the latter of whom reported so many hadeeth on his authority, that they number past a thousand. The scholars agree unanimously upon his reliability and trustworthiness (in the field of hadeeth).
Ibn Hibbaan (rahimahullaah) said of him:
"He was precise and accurate in memory. And he was one of the close companions of Ahmad and Yahyaa Ibn Ma'een."
Al-Khateeb Al-Baghdaadee (rahimahullaah) said:
"He was reliable, trustworthy, possessed good memory and he was precise (in narration)." 
He was born in the year 160H and died in the year 234H. May Allaah have mercy on him.
 This is an ascription to a city that was near Khuraasaan, called Nasaa. People from there attribute themselves to it with "Naswee" also.
 Taareekh Baghdaad (8/482).