What is the authenticity of the hadith narrated on the authority of Ka’b al-Ahbar, in which it is mentioned that "O Moses! Two rak'ahs performed by Ahmed and his Ummah...", to the end of the hadith, and what it includes of virtues for prayer, ablution, fasting, and bearing witness that there is no god but Allah?

This narration attributed to Ka‘b al-Ahbār has not been authenticated. He is one of the narrators upon whom the most lies were fabricated and falsehoods attributed. The aforementioned narration contains clear exaggerations, such as the promise of entering Paradise, whose width is that of the heavens and the earth, for every drop of water from ablution, or granting the reward of thirty martyrs to one who seeks forgiveness regretfully on Laylat al-Qadr (the Night of Decree). One of the indicators of fabrication is the exaggeration of a great reward for a simple act.