Mukhtasar Bukhari

Narrated Abu Huraira (may Allah be pleased with him) from the Prophet (peace and blessings of Allah be upon him) that he said: "Allah Almighty created Adam (peace be upon him) sixty cubits tall, then He said: 'Go! Greet that group of angels and listen to what they reply to you, for that will be your greeting and the greeting of your descendants.' Adam (peace be upon him) said: 'As-salamu alaikum (peace be upon you).' They replied: 'As-salamu alaika wa rahmatullah (peace be upon you and the mercy of Allah).' They added the words 'wa rahmatullah.' So all those who enter Paradise on the Day of Resurrection will be in the form (beauty and stature) of Adam (peace be upon him). (After Adam) the stature of people has been decreasing up to now."