Is stipulating that the husband performs Hajj with the wife valid in a marriage contract?

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The stipulation that the husband must perform Hajj with the wife in the marriage contract is invalid. This position is held by Al-Shafi'i. The reasoning is that the two burdens (the Hajj obligations) are unknown and cannot be definitively limited, thus the stipulation is void, similar to stipulating an unknown dowry. Consequently, the wife is entitled to the dowry equivalent to her peers (mahr al-mithl) in all cases where the specific stipulation is deemed void.