What should I do when I wake up from sleep and am unsure whether ghusl is obligatory for me or not?

If a sleeping person wakes up and sees that they had a wet dream but finds no wetness, then no ghusl (ritual bath) is required of them, by consensus; this is based on the Prophet's (peace be upon him) saying: "If she sees water."

However, if they find wetness, there are three scenarios: 1. They are certain it is semen (mani): Ghusl is obligatory, by consensus. 2. They are certain it is not semen: Ghusl is not obligatory; rather, they should wash whatever was soiled by the wetness, similar to urine. 3. They are unsure whether it is semen (mani) or pre-seminal fluid (madhy): Scholars have differed on this. Al-Nawawi held that ghusl is obligatory to purify from major ritual impurity (janabah) and to purify clothes from impurity. Ahmad and Ibn Taymiyyah held that if it was preceded by thought or foreplay, then it is madhy, and one should sprinkle water on their clothes and no ghusl is required. But if it was not preceded by such, then it is mani, and one must perform ghusl; this is based on the saying of 'Aisha: "The Messenger of Allah (peace be upon him) was asked about a man who finds wetness but does not recall a wet dream? He said: 'He should perform ghusl.' And about a man who sees that he had a wet dream but finds no wetness? He said: 'No ghusl is required of him.'" Both opinions are strong.