Polygamy

It is said that Parashuram continued killing every Kshatriya in his path until there were no more warriors left on earth. 

To restore the Kshatriya clans, the widows married the only left out King Dasarath by Nari-kavacha, meaning 'one whose armor was made of women'. He survived by agreeing to marry them one each day. 

Parashurama had while taking pledge to destroy kshatriyas had restricted himself from killing freshly married couples.