Assalamu alaikum.Saturday is Sabbath day,a day of prayer and celebration for Jews.It is mentioned in Holy Quran and Bible.Was this day made special for Jews by Allah as original Thowrath was revealed for Muslims who later became Jews.Or was this day made special by Jews by their own writings in Bible?Hope you will clarify.Thank you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

It is confirmed in the Sunnah of the Prophet that Allaah ordained the Jews to glorify the day of Friday but they disputed about it, and they had chosen Saturday instead.

Some scholars stated that this day was kept unclear from them and they were left to choose it by themselves but they were wrong in choosing it. However, some other scholars stated that this day was specified for them but they changed it with another day because of their ungratefulness as usual. Whichever view is correct, the result is that it is the Jews who had chosen Saturday and this was not legislated by Allaah for them.

Finally, it should be noted that what you mentioned in the question that the Quran stated the day of festival for the Jews to be Saturday is not correct. Rather, the Quran stated that they transgressed on this day even though they glorified it and believed that it was forbidden to fish during this day. However, they did not act according to what they were ordained to do, and thus instigated the Wrath of Allaah against them, as the scholars stated.