Al-Fath · 48:12

12. The excuse of being preoccupied with taking care of your wealth and children as presented by you was not the reason for remaining behind going out with him. Rather, you thought that the Messenger and his companions will all die and they won't return to their families in Madina. Satan also made this seem fine in your hearts and you had an evil thought about your Lord that He will not help His prophet. You were a ruined people because of the evil thought that you had about Allah and because of your remaining behind His messenger.