What is the ruling on someone who bathed, cleaned their private parts, and then involuntarily discharged a viscous fluid?

If he did not intend to arouse desire, but rather to cleanse himself, then there is no sin upon him for what was discharged, and it is not considered masturbation. If what was discharged was madhy (pre-seminal fluid), it invalidates ablution and requires washing it off and purifying clothes. If it was maniyy (seminal fluid), a full ritual bath (ghusl) is obligatory.