Krishna as you read the Damodar Lila was not bound by mother Yashoda's ropes but because of her pure devotion and love. Whenever she tried to tie with her rope, the rope became less by 2 fingers. She brought more rope and the rope again became less. The she brought more and the rope again was less. So all the ropes of her mansion which housed 900000 lakh cows banished and then also she wasn't able to tie up the Lord. But when Krsna saw the devotion and pain in her mother which was a pure devotee, he himself got tied