Ubayy reported, "The Messenger of Allah ﷺ sent me and said, 'Announce to the people that whoever says, There is no god but Allah, will enter Paradise.'So I went out, and Umar met me on the way and asked, 'Where are you headed?'I replied, 'The Messenger of Allah has sent me with such and such a message.'Umar said, 'Go back.'I refused, so he gave me a shove in my chest, and I had no choice but to return.Umar said, 'Messenger of Allah, did you send this man with such and such a message?'He answered, 'Yes.'Umar said, 'Messenger of Allah, the people will become complacent and stop striving.'So the Prophet ﷺ said, 'Sit down.'"
بعثني رسول الله ﷺ فقال: ناد في الناس: من قال: لا إله إلا الله دخل الجنة فخرج فلقيه عمر في الطريق، فقال: أين تريد؟ قلت بعثني رسول الله بكذا وكذا. قال: ارجع، فأبيت، فلهزني لهزة في صدري فرجعت، ولم أجد بدا. قال: يا رسول الله، بعثت هذا بكذا وكذا؟ قال: نعم. قال: يا رسول الله، إن الناس قد طمعوا وخشوا، فقال النبي ﷺ: اقعد.
Ibn Khuzayma (693) and Ibn Hibban (151) both narrated it through the route of Muharrar bin Qanab Bahili, who said, Rabah bin Ubayda narrated to me, that Zakwan Samman narrated to him, that Jabir bin Abdullah narrated to him and said (then he mentioned it), and the wording is Ibn Hibban's. Its chain is hasan because of Muharrar bin Qanab, for he is hasan al-hadith.