SB 1.17.30

patitaṁ pādayor vīraḥ
 kṛpayā dīna-vatsalaḥ
śaraṇyo nāvadhīc chlokya
 āha cedaṁ hasann iva
Word for word: 
patitam — fallen; pādayoḥ — at the feet; vīraḥ — the hero; kṛpayā — out of compassion; dīna-vatsalaḥ — kind to the poor; śaraṇyaḥ — one who is qualified to accept surrender; na — not; avadhīt — did kill; ślokyaḥ — one who is worthy of being sung; āha — said; ca — also; idam — this; hasan — smiling; iva — like.
Translation: 
Mahārāja Parīkṣit, who was qualified to accept surrender and worthy of being sung in history, did not kill the poor surrendered and fallen Kali, but smiled compassionately, for he was kind to the poor.
Purport: 

Even an ordinary kṣatriya does not kill a surrendered person, and what to speak of Mahārāja Parīkṣit, who was by nature compassionate and kind to the poor. He was smiling because the artificially dressed Kali had disclosed his identity as a lower-class man, and he was thinking how ironic it was that although no one was saved from his sharp sword when he desired to kill, the poor lower-class Kali was spared by his timely surrender. Mahārāja Parīkṣit’s glory and kindness are therefore sung in history. He was a kind and compassionate emperor, fully worthy of accepting surrender even from his enemy. Thus the personality of Kali was saved by the will of providence.