So, I've lived in enough Muslim countries to understand that Friday and Saturday are, in fact, the closest thing there is to a weekend in the US (which would normally be Saturday and Sunday), but what I don't understand is why Muslim services are on Friday?

To be clear, I understand that Saturday is almost universally held as the end of Creation, and the original "Day of Rest." I understand that is why Jews (and some Christian denominations) celebrate their services on Saturday. I understand that in Christianity, however, the "Day of Rest" was celebrated on the day after the Sabbath, celebrating the Resurrection.

What motivated Islam to make Friday, rather than Saturday, its High Holy day of the week?