Sahih Muslim 2841
Abu Huraira reported Allah's Messenger (ﷺ) as saying:
Allah, the Exalted and Glorious, created Adam in His image with His length of sixty cubits, and as He created him He told him to greet that group, and that was a party of angels sitting there, and listen to the response that they give him, for it would form his greeting and that of his offspring. He then went away and said: Peace be upon you! They (the angels) said: May there be peace upon you and the Mercy of Allah, and they made an addition of" Mercy of Allah". So he who would get into Paradise would get in the form of Adam, his length being sixty cubits, then the people who followed him continued to diminish in size up to this day.
حَدَّثَنَا مُحَمَّدُ بْنُ رَافِعٍ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنْ هَمَّامِ بْنِ مُنَبِّهٍ، قَالَ
 هَذَا مَا حَدَّثَنَا بِهِ أَبُو هُرَيْرَةَ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم ‏.‏ فَذَكَرَ أَحَادِيثَ مِنْهَا
 وَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏
"‏ خَلَقَ اللَّهُ عَزَّ وَجَلَّ آدَمَ عَلَى صُورَتِهِ طُولُهُ سِتُّونَ
 ذِرَاعًا فَلَمَّا خَلَقَهُ قَالَ اذْهَبْ فَسَلِّمْ عَلَى أُولَئِكَ النَّفَرِ وَهُمْ نَفَرٌ مِنَ الْمَلاَئِكَةِ جُلُوسٌ فَاسْتَمِعْ
 مَا يُجِيبُونَكَ فَإِنَّهَا تَحِيَّتُكَ وَتَحِيَّةُ ذُرِّيَّتِكَ قَالَ فَذَهَبَ فَقَالَ السَّلاَمُ عَلَيْكُمْ فَقَالُوا السَّلاَمُ
 عَلَيْكَ وَرَحْمَةُ اللَّهِ - قَالَ - فَزَادُوهُ وَرَحْمَةُ اللَّهِ - قَالَ - فَكُلُّ مَنْ يَدْخُلُ الْجَنَّةَ عَلَى صُورَةِ
 آدَمَ وَطُولُهُ سِتُّونَ ذِرَاعًا فَلَمْ يَزَلِ الْخَلْقُ يَنْقُصُ بَعْدَهُ حَتَّى الآنَ ‏"‏ ‏.‏