Sayyiduna Ibn Abbas (may Allah be pleased with them both) says regarding "Allah keeps firm those who believe with the firm word in the life of this world" [Surah Ibrahim: 27]: "This is the questioning in the grave: Who is your Lord? What is your religion? Who is your Prophet? And in the Hereafter there will be questioning likewise."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12190