The Messenger of Allah ﷺ came out to us while we were discussing the Masih Dajjal, and he said, "Shall I not inform you of what I fear for you more than the Masih Dajjal?"We said, "Yes, please."He said, "Hidden polytheism. A man stands to pray and beautifies his prayer because he sees someone watching him."
خرج علينا رسول الله ﷺ ونحن نتذاكر المسيح الدجال، فقال: ألا أخبركم بما هو أخوف عليكم عندي من المسيح الدجال؟ قال: قلنا بلى. فقال: الشرك الخفي: أن يقوم الرجل يصلي فيزين صلاته لما يرى من نظر رجل.
Ibn Majah (4204) narrated it from Abdullah bin Saeed, who said, Abu Khalid Ahmar related to us, from Kathir bin Zayd, from Rabih bin Abdul-Rahman bin Abu Saeed Khudri, from his father, from Abu Saeed, who said, and then he mentioned it. Its chain is hasan because of Rabih bin Abdul-Rahman, about whom there is disagreement, though his hadith is hasan. Abu Zura said, "A shaykh." Ibn Adi said, "I hope there is no harm in him." Ibn Hibban mentioned him among the trustworthy narrators, so his hadith is graded hasan when it has a basis, and this is one such case. Busiri also graded it hasan in Zawaid.Similar in meaning is what was narrated from Abu Musa Ashari, who said, "O people, beware of this shirk, for it is more hidden than the crawling of ants." Abdullah bin Hazn and Qays bin Mudarib stood up to him and said, "By Allah, you must clarify what you said, or we will go to Umar, whether we are permitted or not." He said, "Rather, I will clarify what I said. The Messenger of Allah ﷺ gave us a sermon one day and said, 'O people, beware of this shirk, for it is more hidden than the crawling of ants.'" Someone whom Allah willed to speak said to him, "How can we beware of it when it is more hidden than the crawling of ants, O Messenger of Allah?" He said, "Say, 'O Allah, we seek refuge in You from associating with You anything we know of, and we seek Your forgiveness for what we do not know.'"Ahmad (19606) narrated it, and this is his wording, and Tabarani in Awsat (3503), both through the route of Abdullah bin Numayr, who said, Abdul-Malik, meaning Ibn Abu Sulayman Arzami, related to us, from Abu Ali, a man from Banu Kahil, who said, Abu Musa Ashari gave us a sermon and said, and then he mentioned it. Abu Ali is unknown, and he is among the men of Tajil (1351), narrated from by no one but Abdul-Malik bin Abu Sulayman. Haythami said in Majma (10/224), "Its narrators are the narrators of the sahih, except for Abu Ali, whom Ibn Hibban deemed trustworthy."Similar in meaning is also what was narrated from Abu Bakr Siddiq, which Abu Yaala (58, 59, 60, 61) recorded through several chains, including one through the route of Layth bin Abu Salim, from Abu Muhammad, from Huzaifa, from Abu Bakr, either Huzaifa was present when this occurred with the Prophet ﷺ, or Abu Bakr informed him of it, that the Prophet ﷺ said, "Shirk among you is more hidden than the crawling of ants," and he mentioned other things along with it. This is the first chain, and it contains Layth bin Abu Salim, who was truthful but became confused later in life, and his hadith could not be distinguished, so it was set aside. His shaykh Abu Muhammad is unknown, and Haythami pointed to this in Majma (10/224).The second chain comes through another route from Layth bin Abu Salim, from Abu Muhammad, from Maqil bin Yasar, who said, Abu Bakr related to me from the Prophet ﷺ, and he mentioned the same. This chain, in addition to Layth bin Abu Salim and his shaykh Abu Muhammad, contains Abu Yaala's shaykh Amr bin Husayn, who is discarded as a narrator, and Haythami faulted the chain because of him.The third chain (60, 61) comes through another route from Layth bin Abu Salim, from Abu Muhammad, from Maqil bin Yasar, who said, I witnessed the Prophet ﷺ with Abu Bakr, or he said, Abu Bakr related to me from the Prophet ﷺ, that he said, and this is one of its wordings, "Shirk is more hidden among you than the crawling of ants." Then he said, "Shall I not show you something that removes both its small and great forms from you? Say, 'O Allah, I seek refuge in You from associating with You while I am aware of it, and I seek Your forgiveness for what I am unaware of.'" This chain also contains Layth bin Abu Salim and his shaykh Abu Muhammad.Ibn Jawzi said in Ilal Mutanahiya (2/339), "This hadith was narrated by Layth bin Abu Salim from Abu Muhammad, a shaykh of his, from Huzaifa, from Abu Bakr. At times he says, from Abu Muhammad, from Maqil bin Yasar, and at times he says, from Uthman, from Rafi, from Maqil bin Yasar, from Abu Bakr." Ahmad said, "Layth's hadith is unsettled." Abu Hatim and Abu Zura said, "We do not concern ourselves with him." Ibn Jawzi went on at length in faulting it.Similar in meaning is also what was narrated from Ayesha and Ibn Abbas, though there is discussion regarding both their chains. Nevertheless, the abundance of corroborating narrations indicates that the hadith has a genuine basis. It is therefore obligatory for the Muslim to fear minor shirk, the hidden kind, which is showing off for others.