I was in a gathering in Madinah where Umar bin Khattab was present. He said to one of the men, "So-and-so, how did you hear the Messenger of Allah ﷺ describe Islam?"The man replied, "I heard the Messenger of Allah ﷺ say, 'Islam began as a young camel of one year, then two years, then three, then four, then five, then it reached its full maturity.'"Umar bin Khattab then said, "After full maturity comes nothing but decline."
حدثنا محمد بن جعفر حدثنا عوف قال حدثني علقمة المزني قال
كنت في مجلس فيه عمر بن الخطاب بالمدينة فقال لرجل من القوم يا فلان كيف سمعت رسول الله ﷺ ينعت الإسلام قال سمعت رسول الله ﷺ يقول إن الإسلام بدأ جذعا ثم ثنيا ثم رباعيا ثم سديسيا ثم بازلا قال فقال عمر بن الخطاب فما بعد البزول إلا النقصان
Its isnad is daif, due to the unidentified status of the narrator from the companion. Alqama Muzani is Ibn Abdullah bin Sinan, and he is trustworthy, one of the well-known scholars of Basra. The hadith was also narrated by Abu Yaala, 1/171, no. 1921, and Haythami attributed it to both of them, 7/279, saying that it contains a narrator who is not named, while the rest of its men are trustworthy. However, the hadith is corroborated by what has come regarding Islam having begun as something strange and returning to being strange as it began. It was narrated by Muslim, 1/130, no. 145, Tirmidhi, 5/18, no. 2629, and Ibn Majah in al-Fitan, 2/1320, no. 3988.