I am selling my iphone unlocked jailbroken iphone and need to know what happens if i restore it?

My iphone has a tethered jailbreak and now that i'm selling it I need to erase everything and hand it so that the new owner can have his own account and apps into it. I not sure if restoring it is the right procedure for this and if it is what happens with the device? Would it get locked again?? Please help with answers and guidance.! thank you!!