yad grhyamanair hari-nama-dheyaih
na vikriyetatha yada vikaro
netre jalam gatra-ruhesu harsah
"Certainly that heart is steel-framed which, in spite of chanting the
holy name of the Lord with concentration, does not change when ecstasy
takes place and tears fill the eyes and hairs stand on end."
Tad asma-saram hrdayam batedam. So just like stone or steel does not
melt very easily, similarly, anyone's heart which does not change
after chanting Hare Krsna mantra regularly, the
