For it has been written, RANNI AKARAH LO YALADAH PITZCHI RINNAH V'TZAHALI LO CHALAH KI RABBIM BENEI SHOMEMAH MIB'NEI VE'ULAH (Sing, rejoice, O barren, the one not giving birth, break forth into song and shout for joy, the one not suffering birth pains; because more are the children of the desolate woman than the one having the husband).