What is incumbent upon someone from whom a liquid – a drop – exits after urinating, and he does not know whether it is an illusion or a reality, and it causes him distress in prayer and at work? And how does he purify himself if he is certain that something has exited while he is in the mosque or at work?

It appears the questioner is afflicted with waswasah (obsessive whispering), and he must completely disregard it. Do not enter the toilet to check if something has exited when in doubt; rather, proceed with your worship and pay no mind to the waswas. If you are absolutely certain that something has exited, then you must purify it from your body and clothes, whether you are in the mosque or at work. Avoiding impurity is a condition for the validity of prayer. Unless certainty is achieved, maintain the original state, which is that nothing has exited, for this is what Allah has legislated. Ibn Al-Mubarak said: "If one doubts about hadath (invalidation of ritual purity), he is not obligated to perform wudu' until he is certain, a certainty he can swear by." A man complained to the Prophet, peace and blessings be upon him, that it seemed to him as if he felt something (hadath) during prayer. He (the Prophet) said: "He should not leave until he hears a sound or perceives a smell." This is proof of maintaining the original state, and that purity is a certainty that is not removed except by a similar certainty.