Putting in RAM with a higher speed
The frequency rating on RAM is analogous to the top speed of a car, if it's max speed is (for example) 250 km/h, it can drive up to 250 km/h, but it won't break if u drive at 25 km/h.

Same for RAM. As long as it's the same DDR3 Standard, it will run, regardless of how high the max clock speed is.