Does merely searching for the infallible ones (Ma’soomeen) due to a thought that crossed one’s mind – that the Companion Abdullah ibn Omar lied in order to sleep over at a man’s house – and then sending a question about them, constitute doubt in Islam? And does the ruling of disbelief (Kufr) apply to it, given that the questioner performs all the obligatory duties such as prayer and fasting?

Do not be concerned by the whispers (waswas (definition)) you find in your heart. Rather, your dislike for them is a sign of the soundness of your faith, as Ibn Taymiyyah said that the believer's affliction with the whispers of disbelief that constrict his chest is "pure faith." And whoever's Islam is firmly established with certainty, his Islam will not be removed by doubt. The cure for whispers is to ignore them, seek help from Allah, frequently recite the Quran and perform dhikr (definition), associate with righteous women, and attend gatherings of knowledge.