Al-Hujurat 49:15

Innama almu/minoona allatheenaamanoo billahi warasoolihi thumma lam yartaboowajahadoo bi-amwalihim waanfusihim fee sabeeli Allahiola-ika humu assadiqoon

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.

Believers, in fact, are those who believe in Allah and His Messenger, then have no doubt, and struggle, with their riches and their lives, in the way of Allah. Those are the truthful.