How can it be explained to a Christian friend, who is convinced of Islam but confused by the different schools of thought, that following the Sunnah of the Prophet is the path to salvation?

The Christian should be taught about Islam and encouraged to embrace it, based on the Qur’an and Sunnah, while clarifying Allah’s preservation of His Book and His Prophet’s Sunnah. The Christian should be guided to embrace Islam first, and their mind should not be distracted by differences among Muslims or their shortcomings, for the distinction between Islam as a religion and the behavior of Muslims is clear. Permissible differences among Muslims are those based on ijtihad (independent reasoning) in matters where there is no explicit text or consensus. As for impermissible differences, these are the opposition of sects to Ahlus-Sunnah wal-Jama’ah. It is recommended to invite the Christian to Islam through the creed of Ahlus-Sunnah wal-Jama’ah. It is not permissible to befriend or show affection to a disbeliever; rather, one should treat them kindly, justly, and invite them to guidance.