Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates: The Noble Prophet (peace and blessings be upon him) said: "We have started fighting them, we have not made peace with them, and whoever, out of fear of them, lets any one of them go, he has no relation with us." The Noble Prophet (peace and blessings be upon him) meant snakes.
Hadith Referenceمسند الحميدي / 1190
Hadith Gradingمحدثین:إسناده حسن
Hadith Takhrij«إسناده حسن ،وأخرجه ابن حبان فى «صحيحه» برقم: 5644، وأبو داود فى «سننه» برقم: 5248، وأحمد فى «مسنده» برقم: 7483، 9719، 10892، والبزار فى «مسنده» برقم: 8372، والطحاوي فى «شرح مشكل الآثار» برقم: 1338، 2929، والطبراني فى «الأوسط» برقم: 2113، 6223»
Benefit: In this hadith, the command has been given to kill snakes—that wherever you see one, kill it, even if it is in the Haram (sanctuary). There were some snakes present in Madinah Munawwarah, so the Prophet (sallallahu alayhi wa sallam) had prohibited killing them at that time. However, later on, a general command was given that wherever there is a snake, kill it. Now, this is the ruling; the previous prohibition is abrogated.
Source: Musnad al-Humaydi: Commentary by Muhammad Ibrahim bin Bashir, Page: 1188