The Prophet ﷺ came out and said, "People, beware of the hidden shirk."They asked, "Messenger of Allah, what is the hidden shirk?"He replied, "A man stands to pray and beautifies his prayer, striving to perfect it because he notices people watching him. That is the hidden shirk."In another narration, the Messenger of Allah ﷺ said, "What I fear most for you is the lesser shirk."They asked, "Messenger of Allah, what is the lesser shirk?"He answered, "Showing off. Allah will say to them on the Day of Resurrection, when people are recompensed for their deeds, 'Go to those you used to show off for in the world, and see whether you find any reward with them.'"
خرج النبي ﷺ فقال: أيها الناس إياكم وشرك السرائر قالوا: يا رسول الله، وما شرك السرائر؟ قال: يقوم الرجل فيصلي، فيزين صلاته جاهدا لما يرى من نظر الناس إليه، فذلك شرك السرائر. وفي رواية: أن رسول الله ﷺ قال: إن أخوف ما أخاف عليكم الشرك الأصغر قالوا: يا رسول الله، وما الشرك الأصغر؟ قال: الرياء، يقول الله عز وجل لهم يوم القيامة إذا جزي الناس بأعمالهم: اذهبوا إلى الذين كنتم تراؤون في الدنيا، فانظروا هل تجدون عندهم جزاء.
Ibn Khuzayma (937), Ibn Abu Shayba (8489), Ahmad (23631), Baghawi in Sharh al-Sunnah (4135), and Bayhaqi in Shuab al-Iman (6831) all narrated it through various routes from Asim bin Umar bin Qatada, from Mahmud bin Labeed, who related it. Its chain of transmission is sahih. The first wording belongs to Ibn Khuzayma and Ibn Abu Shayba, and the second wording belongs to Baghawi and Bayhaqi. Imam Ahmad did not present his own wording for this chain, but simply referred back to the wording of the hadith before it.