The Prophet ﷺ said,
“Shall I not inform you what I fear more upon you than the False Messiah.”
People said, ‘Of course, Messenger of Allaah!’ He said,
“The hidden polytheism; that a man stands to pray,
and he beautifies his prayer due to people watching him.” (Ibn Maajah 4203),
and the Prophet ﷺ said,
“O people, fear polytheism! Indeed, it is more hidden than the footsteps of an ant.”
No doubt, if polytheism is this difficult to detect, a person will fall into it without realizing. Then someone asked him, ‘How can we be safe from it when it is more hidden than the footsteps of an ant, Messenger of Allaah, ﷺ?’ He replied,
“Say, Allaahumma innaa na’oothu bika min an-nushrika bika shay’an na’lamuh wa nastaghfiruka lima alaa na’lam!, Allaah, we seek refuge in you from knowingly committing associating partners with you and seek Forgiveness for doing so unknowingly.”
)’Al-Musnad’ hadeeth compilation by Ahmad 19,606)
This shows that there is a type of polytheism that is concealed, and hidden from a person who may fall into it without even noticing.