Answered by Shaykh Faraz Rabbani
Therefore, by deduction, my prayer done sitting in a car because the brother would not stop for me to make Asr (he was getting late) is not valid. Hence, would have to be redone?
Walaikum assalam,
In the case below, one would HAVE to pray because of the inviolability (hurma) of the time, but it would be obligatory to pray again. Of course, all reasonable means would have to be taken to get the brother to stop the car, or, if necessary, to request to get off.
As an aside, it is not permitted to mention things that are sins, even outwardly (i.e. if they were done with a legitimate excuse or excused ignorance). Even when needed, one should either mention the issue without mentioning oneself, or mention oneself, but only privately, as fuqaha have mentioned.
Wassalam,
Faraz