Surah Al-Hujurat 49:15

إِنَّمَا ٱلْمُؤْمِنُونَ ٱلَّذِينَ ءَامَنُوا۟ بِٱللَّهِ وَرَسُولِهِۦ ثُمَّ لَمْ يَرْتَابُوا۟ وَجَـٰهَدُوا۟ بِأَمْوَٰلِهِمْ وَأَنفُسِهِمْ فِى سَبِيلِ ٱللَّهِ ۚ أُو۟لَـٰٓئِكَ هُمُ ٱلصَّـٰدِقُونَ

The believers are only the ones who have believed in Allāh and His Messenger and then doubt not but strive with their properties and their lives in the cause of Allāh. It is those who are the truthful.

Translation: Saheeh International

Tafsir

The true believers that is those who are true in their affirmation of faith — as He makes explicit in what follows — are only those who believe in God and His Messenger and then have not doubted they have not been uncertain of their faith and who strive with their wealth and their souls for the cause of God hence …

Excerpt from Tafsir al-Jalalayn, commentary on 49:15, via Quran.com. The reader has the full commentary and 9 more tafsirs.