Zadhan Abu Umar narrates: Someone who heard the Prophet (peace and blessings be upon him) say this narrated it to me: "Whoever is prompted at the time of death to say 'La ilaha illallah' (There is no god but Allah) will enter Paradise."
Ahmad recorded it. Its chain contains Ata' bin al-Sa'ib, who has been criticised because of his ikhtilat (deterioration of memory).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الجنائز / 3908