5r5 is a way to promise someone that what you're telling them is 100% serious. And that you are not joking in any way about what you're saying.
Dave: Devin, lets play Halo.
Devin: I can't, I am going to a girls house.
Dave: Yeah right.
5r5 (5od ra7tak/5ody ra7tek 5ales) is the Egyptian alternative contraction for tyt (take your time)