The example of the idolaters who took idols whom they worshipped other than Allah in the hope that they will benefit them or intercede for them is like that of a spider that builds a house to protect it from heat and cold and from an assault against it. The frailest of all houses is the spider’s as it does not ward off any cold nor prevent any heat. Similarly, their idols will not benefit nor harm nor intercede. If the idolaters knew that, they would not have taken idols that they worship besides Allah.

The parable of those who seek protectors from other than Allah is that of a spider who builds a house; but indeed, the weakest of houses is the spider's house – if they but knew (41)Verily, Allah knows what things they invoke instead of Him. He is the All-Mighty, the All-Wise (42)And these are the examples We give for mankind; but none will understand them except those who have knowledge (of Allah)(43)

This is how Allah described the idolators in their reverence of gods besides Him, hoping that they would help them and provide for them, and turning to them in times of difficulties. In this regard, they were like the house of a spider, which is so weak and frail, because by clinging to these gods they were like a person who holds on to a spider's web, who does not gain any benefit from that. If they knew this, they would not take any protectors besides Allah. This is unlike the Muslim believer, whose heart is devoted to Allah, yet he still does righteous deeds and follows the Laws of Allah, for he has grasped the most trustworthy handle that will never break because it is so strong and firm.

Then Allah warns those who worship others besides Him and associate others with Him that He knows what they do and the rivals they associate with Him. He will punish them for their attribution, for He is All-Wise and All-Knowing. Then He says:

وَتِلْكَ الْأَمْثَالُ نَضْرِبُهَا لِلنَّاسِ ۖ وَمَا يَعْقِلُهَا إِلَّا الْعَالِمُونَ 

(And these are the examples We give for mankind; but none will understand them except those who have knowledge.) meaning, no one understands them or ponders them except those who are possessed of deep knowledge. Ibn Abi Hatim recorded that 'Amr bin Murrah said, "I never came across an Ayah of the Book of Allah that I did not know, but it grieved me, because I heard that Allah says:

وَتِلْكَ الْأَمْثَالُ نَضْرِبُهَا لِلنَّاسِ ۖ وَمَا يَعْقِلُهَا إِلَّا الْعَالِمُونَ 

(And these are the examples We give for mankind; but none will understand them except those who have knowledge.)"

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)

It is shown here that one who sees a spider’s web and learns a lesson about reality from it, is a learned person in the true sense. This clealy demonstrates who are the truly learned in the eyes of God. They are not those who have become expert in bookish discourses, but individuals who are capable of imbibing the sound advice given by God’s signs scattered throughout His world, and whose minds are capable of magnifying small events into great lessons. When this very learning reaches the final stage of ma‘rifah or ‘knowledge with intense realization of God,’ then it is called by its other name: faith or iman.