Because of mother Yashoda's hard labor, her whole body became covered with perspiration, and the flowers were falling from her hair.
When child Krishna saw His mother thus fatigued, He became merciful to her and agreed to be bound.
Thus there was a competition between a devotee and Krishna.
In the end, seeing His devotee's total unalloyed determination to tie Him, Krishna had to accept defeat.
In this way, mother Yashoda tied Him to a wooden grinding mortar.
Buuks Sri damodar lila, paperback/sri srimad radha govinda das goswami
