Exodus 19:6 And ye shall be unto me a kingdom of priests , and an holy nation. These are the words which thou shalt speak unto the children of Israel. (Note that this is the only place in the KJV that the scripture says "kingdom of priests". In Rev. 1:6 & 5:10 the wording is 'kings and priests')
Revelation 1:6 And hath made us kings and priests unto God and his Father; to him be glory and dominion for ever and ever. Amen.
Revelation 5:19 And hast made us unto our God kings and priests : and we shall reign on the earth.