evam āvedito rājā
jahāsoccaiḥ sma māgadhaḥ
āha cāmarṣito mandā
yuddhaḿ tarhi dadāmi vaḥ
evam -- thus; aveditah -- invited; raja -- the King; jahasa -- laughed; uccaih -- out loud; sma -- indeed; magadhah -- Jarasandha; aha -- he said; ca -- and; amarshitah -- intolerant; mandah -- O fools; yuddham -- battle; tarhi -- then; dadami -- I will give; vah -- to you.
Srila Visvanatha Cakravarti comments that Jarasandha felt inner satisfaction because he thought that his enemies had been humiliated by having to dress like brahmanas to approach him. Thus the acarya understands Jarasandha's mind as follows: "O weak ones, forget the botheration of fighting. Why not just accept my head? By dressing yourselves as brahmanas begging charity, you have made your heroism set like the sun, but if somehow you have not lost your courage, I will give you battle."
The acarya finally points out that the goddess of learning intends the phrase amarshito mandah to read amarshito 'mandah. In other words, Lord Krishna and the Pandavas are amandah, "never foolish." And that is why they chose the best tactic for doing away once and for all with the cruel Jarasandha.