Is the prayer of one who is forced to go out and prays sitting so as not to miss the prayer invalid?

Standing in the obligatory prayer is an agreed-upon pillar. The prayer of one who is able to stand but sits is not valid. Whoever deems it permissible to sit without an excuse has committed disbelief. Some Muslims in lands of disbelief may pray the obligatory prayer sitting out of shyness from people or due to the absence of a suitable place, but this is not an excuse, for the entire earth is a mosque. Whoever prays in such a manner, their prayer is invalid and must be repeated.