Acts 10

And those of the circumcision who believed were astonished, as many as came with Peter, because the gift of the Holy Spirit had been poured out on the Gentiles also. v.45

Read chapter 10
Cornelius and his household are the first non-Jews to receive the Holy Spirit.  Cornelius wasn't just any gentile but one who feared God and worked righteousness (v.35).  He knew as much as he could know about the God of Israel sent a whole lost as it wasn't just a religion  someone could "try out" or be converted to.  But with the little he saw and knew he believed and followed that in his actions seeing his whole being a centurion of the Italian Regiment probe had more than just his family living in his household.  He had a contagious influence probably on his servants and other workers too.  
We today aren't all Jews and there are some promises for Jews that aren't for gentiles and there are some that are blessings for both.  But no matter what we should fear God and let that shine on those who dwell among us that tit'll be contagious too.