tato 'muñcac chilā-varṣaḿ
balasyopary amarṣitaḥ
tat sarvaḿ cūrṇayāḿ āsa
līlayā muṣalāyudhaḥ
tatah -- then; amuncat -- he released; sila -- of stones; varsham -- a rain; balasya upari -- on top of Lord Balarama; amarshitah -- frustrated; tat -- that; sarvam -- all; curnayam asa -- pulverized; lilaya -- easily; mushala-ayudhah -- the wielder of the club.
Srila Prabhupada writes, "When no more trees were available, Dvivida took help from the hills and threw large pieces of stone, like rainfall, upon the body of Balarama. Lord Balarama, in a great sporting mood, began to smash those big pieces of stone into mere pebbles." Even today there are many sports wherein people enjoy striking a ball or similar object with a stick or bat. This sporting propensity exists originally in the Supreme Personality of Godhead, who playfully (lilaya) pulverized the deadly boulders hurled at Him by the powerful Dvivida.