On the authority of ʿAbd Allah ibn ʿAmr (may Allah be pleased with them both), the Messenger of Allah, peace and blessings be upon him, said:

“None of you truly believes until his inclination follows that which I have brought.”

Al-Nawawi commented, “This is an authentic hadith; we transmitted it in the book Al-Hujjah with a sound chain of narration.” (1)

Biographical notes
• Al-Nawawi: Muḥy al-Dīn Abū Zakariyyā Yaḥyā ibn Sharaf al-Nawawi—named after the village of Nawa in Greater Syria—was a celebrated imam and prolific author. He died in 676 AH.
• Al-Hujjah: i.e. the work Al-Hujjah ʿalā Tārik al-Mahajjah by Shaykh Abū ’l-Fath Naṣr ibn Ibrāhīm al-Maqdisī al-Shāfiʿī.

Although the chain of this hadith has been challenged, its meaning is unquestionably sound even if the isnad itself is not. It is corroborated by Qur’anic evidence, such as Allah’s words:
“But no, by your Lord, they will not believe until they make you judge concerning that over which they dispute among themselves and then find within themselves no discomfort from what you have decided and submit in complete submission.” (al-Nisaʾ 4:65)

“No one of you believes” – he does not attain the obligatory level of faith nor belong to its people.

“His inclination” – whatever the soul desires, loves, and leans toward.

“Follows what I have brought” – he loves what the Messenger ﷺ commanded and hates what he forbade.

The overall meaning of the hadith: a person is not considered a believer in the requisite faith