Shiva Purana
हंतव्योऽपि न हंतव्यः पानीयं यश्च याचते॥ रणे हत्वातुरान्व्यास स नरो ब्रह्महा भवेत् ॥ ३६॥
Even a murderer shall not be attacked and killed if he is thirsty and begs for water. O Vyāsa, by killing the sick and the distressed even in battle a man becomes guilty of brahminicide.
english translation
haMtavyo'pi na haMtavyaH pAnIyaM yazca yAcate॥ raNe hatvAturAnvyAsa sa naro brahmahA bhavet ॥ 36॥
hk transliteration by Sanscript