It's exactly the opposite. Friction is what makes sure that the core and the outer parts of the Earth keep on rotating together at the same angular velocity. Earth's core is essentially co-rotating with the rest of the Earth. read more
So, to repeat, the existence of friction between the ocean, the crust, the mantle, and the outer and the inner core is exactly the thing which guarantees that, as the Earth's rotation gradually slows down, all portions of the Earth keep on co-rotating with each other. read more
Earth is rotating in the vacuum of space so there is no friction to slow it down. However the tidal forces of the moon and sun do slow the rotation but only by a few milliseconds per century. Occasionally earthquakes have caused tiny increases as well as decreases. read more
Currently, the rotation of Earth is faster than the moon, which results in the moon slowly moving away from Earth. If the rotation stops, the moon will start to move towards Earth, and it would eventually cause Earth to start rotating again. read more