Is ghusl obligatory if, upon waking, a light, non-viscous, yellowish discharge is emitted? And is it a condition that all three characteristics of semen (yellow color, viscosity, gushing, and post-ejaculatory flaccidity) be present, or is the presence of some of them sufficient for it to be considered semen?

If a sleeping person wakes up and finds moisture, there are three scenarios:

1. If he is certain it is manī (seminal fluid), then ghusl (ritual bath) is obligatory, whether he recalls a wet dream or not.

2. If he is certain it is not manī, then ghusl is not obligatory; rather, he should wash what it has touched.

3. If he is unsure whether it is manī or not:

If he recalls a wet dream in his sleep, it makes it manī, and he must perform ghusl.

If he saw nothing in his dream, but prior to sleeping he had thoughts of intercourse, it makes it madhy (pre-seminal fluid).

If he had no prior thoughts before sleeping, then ghusl is not obligatory according to the majority of scholars, and this is the most correct opinion, because the original state is the absence of obligation.