Sayyiduna Bara bin Azib (may Allah be pleased with him) narrates this statement of the Prophet (peace and blessings be upon him): "When a believer testifies in the grave that there is no deity except Allah and recognizes Sayyiduna Muhammad (peace and blessings be upon him), then this is what is meant by Allah Almighty's statement: 'Allah will keep the believers firm with the firm word in the life of this world and in the Hereafter.'"
Hadith Referenceصحیح ابن حبان / كتاب التاريخ / 6324
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - مضى (206).فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط البخاري