question #1 Sahih al-Bukhari 4085, Book 64, Hadith 129 : What concerns did the Prophet Muhammad (ﷺ) express about the future behavior of his followers after his passing?

One day the Prophet (ﷺ) went out and offered the (funeral) prayer for the people (i.e. martyrs) of Uhud as
he used to offer a funeral prayer for any dead person, and then (after returning) he ascended the pulpit
and said, “I am your predecessor before you, and I am a witness upon you, and I am looking at my
Tank just now, and I have been given the keys of the treasures of the world (or the keys of the world).
By Allah, I am not afraid that you will worship others besides Allah after me, but I am afraid that you
will compete with each other for (the pleasures of) this world.”