What is the supplication of mutual cursing (li'an)? And what are its conditions?

The traditional supplication for someone who awakens at night is to say: "There is no god but Allah, He is alone, He has no partner, to Him belongs the dominion, and to Him belongs all praise, and He is over all things competent. All praise is due to Allah, and glory be to Allah, and there is no god but Allah, and Allah is the Greatest, and there is no power nor might except with Allah." Then he should say: "O Allah, forgive me," or supplicate. There are also additions such as: "the Most High, the Most Great," and "He gives life and causes death, in His hand is all good, and He is over all things competent."

A condition for this supplication is that the person should have gone to bed in a state of purity, and that he should remember Allah upon waking without speaking any other words. It is preferred that this be for someone who is accustomed to remembrance and feels at ease with it.