وَإِنَّ أَوْهَنَ الْبُيُوتِ لَبَيْتُ الْعَنكَبُوتِ (And surely the weakest of houses is the house of the spider - 29:41). ` Ankabut (عَنكَبُوتِ ) is the Arabic language equivalent for spider. There are different species of spiders. Some of them live underground. Apparently those are not meant here. Instead the specie of spider meant here is the one which weaves web for itself, and stays suspended in it. It attracts and kills flies in the cobweb. Among all the known types of nests, dens and other abodes of animals, the spider's web is the weakest. Even a mild breeze can break its threads. This verse has described those who worship and place their trust in any one other than Allah, are like the web of spider, which is extremely weak. The trust of those who depend on idols or any human is as weak and fragile as the trust of a spider on its web.
Ruling
Scholars have different viewpoints in the matter of killing of spiders and removing of cobwebs from the houses. Some do not like it, because at the time of hijrah the spider weaved its web at the mouth of the cave Thaur, and thus made a place of respect for itself. Khatib has reported that Sayyidna ` Ali ؓ had prohibited its killing. But Tha` labi and Ibn ` Atiyyah have quoted a narration, again from Sayyidna ` Ali رضی اللہ تعالیٰ عنہ that says طَھِّرُوا بُیُوتَکُم مِّن نَسجِ العَنکَبُوتِ فَاِنَّ ترکَہ، یُورثُ الفَقَر (Clean your homes from the web of the spider, because its retaining causes poverty.) The chain of the narrators of both these reports is not reliable, but the second narration draws credence from other narrations in which keeping of homes clean is stressed. (Ruh u1-Mani)