Praise be to Allah.
It is commanded to kill the wazagh, and the reason for that is that they are noxious little creatures [fuwaysiq]. It is also commanded to kill other vermin, such as snakes, scorpions and vicious dogs.
Al-Bukhaari (1831) narrated from ‘Aa’ishah – the wife of the Prophet (blessings and peace of Allah be upon him) – that the Messenger of Allah (blessings and peace of Allah be upon him) called the wazagh a noxious little creature, but I did not hear him enjoin killing it.
Muslim (2238) narrated from Sa‘d, from his father, that the Prophet (blessings and peace of Allah be upon him) enjoined killing the wazagh and called it a noxious little creature. The reason why it is to be killed is that it is harmful.
Ad-Dumayri said in Hayaat al-Haywaan al-Kubraa (2/546): With regard to calling the wazagh a noxious little creature [fuwaysiq], it is similar to the five vermin [al-fawaasiq al-khams] that may be killed both outside and within the Haram zone. The root meaning of fisq [from which the word fuwaysiq (noxious little creature) is derived] is to drift away, and these creatures have drifted away from the characteristics of most other similar animals, because they cause much greater harm. End quote.
Al-Bukhaari (3359) narrated from Umm Shareek (may Allah be pleased with her) that the Messenger of Allah (blessings and peace of Allah be upon him) enjoined killing the wazagh and said: “It used to blow on (the fire of) Ibraaheem (peace be upon him).”
Al-Mulla ‘Ali al-Qaari (may Allah have mercy on him) said, commenting on this hadith:
The Messenger of Allah (blessings and peace of Allah be upon him) enjoined killing the wazagh lizard.
It is a small and harmful creature.
The Prophet (blessings and peace of Allah be upon him) said: “It used to blow on (the fire of) Ibraaheem”; that is, the fire that was beneath him.
Al-Qaadi said: This highlights the evil of this type of animal and the harm that it causes, as its evil reached such an extent that the Shaytaan used it and prompted it to blow into the fire into which Ibraaheem (peace be upon him) was thrown, and it tried to make the fire flare up, so in general it is one of the venomous and harmful creatures.
Ibn al-Malak said: It [the wazagh] is very keen to spoil food, especially salt. If it finds no other way to spoil it, it climbs up to the ceiling and drops its feces onto it. This hadith explains that its nature is to cause harm.
End quote from Mirqaat al-Mafaateeh (7/2671).
The words “It used to blow on (the fire of) Ibraaheem” indicate that it is innately evil and harmful, but that is not the only reason for killing it.
Ash-Shirwaani (may Allah have mercy on him) [a Shaafa‘i scholar] said:
That is, because its ancestor was the one who blew onto the fire, which affirms the evil nature of this type of creature, by way of honouring Ibraaheem.
End quote from Haashiyat Tuhfat al-Muhtaaj (9/383).
Among the harms of this creature that were mentioned by the scholars, it spits into vessels, as a result of which man is exposed to a great deal of harm, as is stated in ‘Umdat al-Qaari (15/250).
It is venomous and spits out venom, and it transmits serious diseases to those with whom it lives.
An-Nawawi (may Allah have mercy on him) said, explaining the reason for killing it: The scholars are agreed that the wazagh comes under the heading of harmful vermin.
The Prophet (blessings and peace of Allah be upon him) enjoined killing it, and urged and encouraged people to do so, because it is harmful.
End quote from Sharh Muslim (14/236).
The wazagh is not to be killed because of the sin of its ancestor; rather it is to be killed because it is harmful. Those that are found in houses and those that are found on farms are the same.
Regarding the reward for killing this noxious little creature, Muslim (2240) narrated that Abu Hurayrah said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever kills a wazagh with the first blow will have such and such of hasanah. Whoever kills it with the second blow will have such and such of hasanah, less than the first. Whoever kills it with the third blow will have such and such of hasanah, less than the second.”
And Allah knows best.