Musnad Ahmad 30:1052

And the Messenger of Allah, may Allah bless him and grant him peace, said: "Allah, the Almighty and Majestic, created Adam in His image, his height being sixty cubits. When He created him, He said to him: 'Go and greet those people'—and they were a group of angels sitting—'and listen to what they answer you, for it is your greeting and the greeting of your descendants.' He said: 'So he went and said: "Peace be upon you (As-salamu alaykum)." They said: "Peace be upon you and the mercy of Allah (As-salamu alayka wa rahmatullah)." So they added to it: "and the mercy of Allah."' He said: 'Everyone who enters Paradise will be in the image of Adam, and his height will be sixty cubits. And creation has continued to diminish ever since until now.'"