What is the basis for requiring Qada for forced intercourse, despite lack of consent?

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The primary rationale for requiring the make-up fast (Qada) for forced intercourse is that it constitutes sexual penetration (Jima') in the private parts, which invalidates the fast, similar to intercourse performed under the duress of a threat. Furthermore, sexual intercourse is a fundamental act that invalidates the fast, just as it invalidates prayer and Hajj, unlike eating, which is excused if done out of forgetfulness.