Kumar extended greetings on the occasion and prayed for peace, amity and brotherhood in the society.
"I pray that Bihar moves forward with harmony," Kumar told reporters at his residence where the Iftar was hosted.
Lalu Prasad Yadav said Muslims along with Hindus pray to the almighty at some places.
Everybody should move ahead with feeling of peace and brotherhood, Prasad told reporters on the occasion.
Lalu's sons - Deputy Chief Minister Tejashwi Yadav and Health Minister Tej Pratap - and wife Rabri Devi also attended the Iftar party.