What should a worshiper recite during the Tashahhud if they have not memorized it? And is it obligatory to research every Hadith about which scholars have differed regarding its authentication or weakening, and to adopt the opinion of the most knowledgeable? And how does one determine who was the most knowledgeable among past scholars?

The final Tashahhud is a pillar of prayer, and it is obligatory to learn it. If it is impossible to learn it, or if time is short, the worshipper should recite its substitute, which is Tasbih (subhanallah), Tahmid (alhamdulillah), Tahlil (la ilaha illallah), and Takbir (Allahu akbar). It is preferable that it include Tawhid (affirmation of God's Oneness) and praise of Allah. If one is able to read it from a paper or phone, etc., it is obligatory to do so, and this takes precedence over reciting the substitute. Every Muslim must gain a deep understanding of their prayer and learn what is necessary in it, and those around them should teach the ignorant.

If scholars differ on authenticating or weakening a hadith, it is permissible to follow one of the trustworthy scholars, or to ask the people of knowledge in hadith and adopt their opinion. For those who have the ability to research and examine, they may strive to determine what is most likely correct.