Voluntarily slave ? allowed or Not ? a clear ayah or Hadith can some one mention pls

Asslamwalekum WRB my question is we do not find any Hadith that mention anything about voluntary enslavement, yes you will find some Hadith that talks about how it was offer to Zaid R.A to be free but he chooses to be a slave , even I ayah of Qur'an as much as I read and researched no such Ayah that says if some non muslim wants to be voluntarily slave for better life or getting out from a very rusty and filthy life is prohibited or any thereof this sort , can some one please enlight me , will be grateful thanks , jajakallah thanks