Reference : Hisn al-Muslim 35

سُبـّوحٌ قُـدّْوس ، رَبُّ الملائِكَـةِ وَالـرُّوح
Subbūḥun, Quddūsun, Rabbul-malā'ikati warrūḥ.

Glory (to You) , Most Holy (are You) , 
Lord of the angels and the Spirit.

Reference:
Muslim 1/353, Abu Dawud 1/230.

Chapter: While bowing in prayer