We (Muslims) are the last (to come) but (will be) the foremost on the Day of Resurrection And this was their day (Friday) of celebration

Narrated Abu Huraira (May Allah Subhanahu wa ta'ala be pleased with him) -

I heard Allah's Apostle (May Peace,blessings and mercy of Allah Subhanahu wa ta'ala be on him) saying, "We (Muslims) are the last (to come) but (will be) the foremost on the Day of Resurrection though the former nations were given the Holy Scriptures before us. And this was their day (Friday) the celebration of which was made compulsory for them but they differed about it. So Allah gave us the guidance for it (Friday) and all the other people are behind us in this respect: the Jews' (holy day is) tomorrow (i.e. Saturday) and the Christians' (is) the day after tomorrow (i.e. Sunday)."

Sahih Bukhari:Volume 2, Book 13, Number 1