How authentic is the attribution of the saying to Umar ibn Al-Khattab, may Allah be pleased with him, regarding the incident of the Ifk (slander): "Do you think that your Lord deluded you in it?"?

This narration has no known origin, and Al-Muhibb Al-Tabari mentioned it without a chain of narration. What indicates its lack of authenticity is the well-known account that this Tasbeeh (exclamation of 'Subhanallah') was uttered by a man from the Ansar, as reported by Al-Bukhari from Aisha, that the Messenger of Allah, peace and blessings be upon him, said: "What do you suggest regarding people who are slandering my family? I have never known anything bad about them." Then a man from the Ansar said: "Glory be to You! {It is not for us to speak of this. Glory be to You, this is a great slander}." It has been mentioned in some narrations that this Ansari was Abu Ayyub Al-Ansari, and it has also been reported that someone else said it. Al-Hafiz Ibn Hajar referred to these narrations and did not mention anything about 'Umar's agreement.