ما هي كفارة من نذر ألا يعصي الله مدى الحياة، ويعلم أنه لن يستطيع الوفاء بذلك؟

A vow to abandon sin reaffirms the obligation to abandon it. If the sin is committed, seeking forgiveness (istighfar) and repentance (tawbah) becomes obligatory. However, according to the majority of scholars, expiation (kaffarah) is not required because a vow to abandon what is already forbidden is not valid, and it is not permissible to commit oneself to something that is already obligatory.