The Prophet ﷺ said, "Allah created Adam in His image, his height being sixty cubits. When He had created him, He said, 'Go and greet that group of angels who are seated, and listen to how they greet you in return, for that will be your greeting and the greeting of your descendants.'So Adam said, 'Peace be upon you,' and they replied, 'Peace be upon you and the mercy of Allah.' They added, 'and the mercy of Allah.'Everyone who enters Paradise will be in the form of Adam. Mankind has continued to diminish in stature ever since, until now."
عن النبي ﷺ قال: خلق الله آدم على صورته، طوله ستون ذراعا، فلما خلقه قال: اذهب فسلم على أولئك النفر من الملائكة جلوس، فاستمع ما يحيونك، فإنها تحيتك وتحية ذريتك، فقال: السلام عليكم، فقالوا: السلام عليك ورحمة الله، فزادوه: ورحمة الله، فكل من يدخل الجنة على صورة آدم، فلم يزل الخلق ينقص بعد حتى الآن.
Bukhari narrated it in the Book of Seeking Permission (6227), and Muslim in the Book of Paradise and Its Description of Bliss (2841), both via Abdul-Razzaq, from Mamar, from Hammam, from Abu Hurairah, who mentioned it.