📖 Abu Sa’eed Al-Khudri RadhiAllahu 'anhu narrated: The Messenger of Allah SallAllahu 'alaihi wa sallam came to us while we were discussing the False Messiah (the dajjaal).
The Prophet SallAllahu 'alaihi wa sallam said, “Shall I not tell you about my greater fear for you than the False Messiah?” We said, “Of course!” The Prophet SallAllahu 'alaihi wa sallam said, “It is hidden idolatry (inconspicuous shirk/polytheism), that a man stands for prayer and beautifies his prayer when he sees another man looking at him.”
Source: Sunan Ibn Mājah 4204
Grade: Hasan (Fair) according to Al-Albani
📖 Ma’qil ibn Yasar RadhiAllahu 'anhu narrated: I departed with Abu Bakr RadhiAllahu 'anhu to meet the Prophet Muhammad SallAllahu 'alaihi wa sallam. The Messenger Muhammad SallAllahu 'alaihi wa sallam said, “O Abu Bakr, there is (polytheism/shirk) idolatry among you more hidden than the crawling of an ant.” Abu Bakr RadhiAllahu 'anhu said, “Is there idolatry other than to make another god alongside Allah?” The Prophet SallAllahu 'alaihi wa sallam said, “By the One in Whose Hand is my soul, there is idolatry more hidden than the crawling of an ant. Shall I not tell you something to say to rid you of it both minor and major? Say: "O Allah, I seek refuge in You that I associate partners with You while I know, and I seek Your Forgiveness for what I do not know."”
Source: Al-Adab Al-Mufrad 715
Grade: Sahih (Authentic) according to Al-Albani
https://preciousgemsfromthequranandsunnah.wordpress.com/2018/12/16/dua-for-protection-from-shirk-a-very-important-dua/