What is the ruling on asking a person if he has prayed or not, and demanding that he swear by Allah to prove his truthfulness in that, and what are the evidences for its prohibition if it is indeed prohibited?

It is permissible for a Muslim to ask his brother, "Have you prayed?" to remind him if he has forgotten it, and the Prophet, peace and blessings be upon him, did this with a Companion. This question is commendable, especially if the questioner is a guardian of the one being asked, but with caution against excessive questioning of the general public, lest it suggest surveillance or accuse them of negligence. One should not make them swear an oath, for the basic principle regarding a Muslim is truthfulness, and making someone swear an oath implies suspicion and corrupting doubt, as stated in the hadith (definition): "If you follow suspicion among people, you will corrupt them."