He prevented ejaculation; does he have to do ghusl?

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Check below answers in case you are looking for other related questions:
Is it obligatory to do ghusl after being manually stimulated?
If maniy (semen) is emitted whilst one is awake because of illness, ghusl is not required

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Related Answers:
If a female has an orgasm without intercourse
Is it necessary for husband and wife to perform ghusl straight after intercourse?
He bathed in seawater; does that take the place of wudoo’?
Is it obligatory to do ghusl after being manually stimulated?
If maniy (semen) is emitted whilst one is awake because of illness, ghusl is not required

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