The Prophet ﷺ said, "Allah created Adam, making him 60 cubits tall. When He created him, He said to him, "Go and greet that group of angels, and listen to their reply, for it will be your greeting (salutation) and the greeting (salutations of your offspring." So, Adam said (to the angels), As-Salamu Alaikum (i.e. Peace be upon you). The angels said, "As-salamu Alaika wa Rahmatu-l-lahi" (i.e. Peace and Allah's Mercy be upon you). Thus the angels added to Adam's salutation the expression, 'Wa Rahmatu-l-lahi,' Any person who will enter Paradise will resemble Adam (in appearance and figure). People have been decreasing in stature since Adam's creation.  

عَنِ النَّبِيِّ ﷺ قَالَ خَلَقَ اللَّهُ آدَمَ وَطُولُهُ سِتُّونَ ذِرَاعًا ثُمَّ قَالَ اذْهَبْ فَسَلِّمْ عَلَى أُولَئِكَ مِنَ الْمَلاَئِكَةِ فَاسْتَمِعْ مَا يُحَيُّونَكَ تَحِيَّتُكَ وَتَحِيَّةُ ذُرِّيَّتِكَ فَقَالَ السَّلاَمُ عَلَيْكُمْ فَقَالُوا السَّلاَمُ عَلَيْكَ وَرَحْمَةُ اللَّهِ فَزَادُوهُ وَرَحْمَةُ اللَّهِ فَكُلُّ مَنْ يَدْخُلُ الْجَنَّةَ عَلَى صُورَةِ آدَمَ فَلَمْ يَزَلِ الْخَلْقُ يَنْقُصُ حَتَّى الآنَ  

The Prophet ﷺ said, "Allah created Adam in His picture, sixty cubits (about 30 meters) in height. When He created him, He said (to him), "Go and greet that group of angels sitting there, and listen what they will say in reply to you, for that will be your greeting and the greeting of your offspring." Adam (went and) said, 'As-Salamu alaikum (Peace be upon you).' They replied, 'AsSalamu-'Alaika wa Rahmatullah (Peace and Allah's Mercy be on you) So they increased 'Wa Rahmatullah' The Prophet ﷺ added 'So whoever will enter Paradise, will be of the shape and picture of Adam Since then the creation of Adam's (offspring) (i.e. stature of human beings is being diminished continuously) to the present time."  

عَنِ النَّبِيِّ ﷺ قَالَ خَلَقَ اللَّهُ آدَمَ عَلَى صُورَتِهِ طُولُهُ سِتُّونَ ذِرَاعًا فَلَمَّا خَلَقَهُ قَالَ اذْهَبْ فَسَلِّمْ عَلَى أُولَئِكَ النَّفَرِ مِنَ الْمَلاَئِكَةِ جُلُوسٌ فَاسْتَمِعْ مَا يُحَيُّونَكَ فَإِنَّهَا تَحِيَّتُكَ وَتَحِيَّةُ ذُرِّيَّتِكَ فَقَالَ السَّلاَمُ عَلَيْكُمْ فَقَالُوا السَّلاَمُ عَلَيْكَ وَرَحْمَةُ اللَّهِ فَزَادُوهُ وَرَحْمَةُ اللَّهِ فَكُلُّ مَنْ يَدْخُلُ الْجَنَّةَ عَلَى صُورَةِ آدَمَ فَلَمْ يَزَلِ الْخَلْقُ يَنْقُصُ بَعْدُ حَتَّى الآنَ  

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. (Using translation from Muslim 2841)  

وَقَالَ رَسُولُ اللهِ ﷺ خَلَقَ اللهُ ﷻ آدَمَ عَلَى صُورَتِهِ طُولُهُ سِتُّونَ ذِرَاعًا فَلَمَّا خَلَقَهُ قَالَ لَهُ اذْهَبْ فَسَلِّمْ عَلَى أُولَئِكَ النَّفَرِ وَهُمْ نَفَرٌ مِنَ الْمَلَائِكَةِ جُلُوسٌ فَاسْتَمِعْ مَا يُجِيبُونَكَ فَإِنَّهَا تَحِيَّتُكَ وَتَحِيَّةُ ذُرِّيَّتِكَ قَالَ فَذَهَبَ فَقَالَ السَّلَامُ عَلَيْكُمْ فَقَالُوا السَّلَامُ عَلَيْكَ وَرَحْمَةُ اللهِ فَزَادُوهُ وَرَحْمَةُ اللهِ قَالَ فَكُلُّ مَنْ يَدْخُلُ الْجَنَّةَ عَلَى صُورَةِ آدَمَ وَطُولُهُ سِتُّونَ ذِرَاعًا فَلَمْ يَزَلْ يَنْقُصُ الْخَلْقُ بَعْدُ حَتَّى الْآنَ  

"خَلَقَ اللَّه آدمَ عَلَى صُورَتِهِ، وَطُولُهُ سِتُّونَ ذِرَاعًا ثُمَّ قَالَ: اذْهَبْ فَسَلِّمْ عَلَى أُولئِكَ النَّفِر، وَهُمْ نفرٌ مِنَ الْمَلاِئِكَةِ جُلُوسٌ، وَاسْتَمِعْ مَا يُحَيُّونَكَ؛ فَإِنَّهَا تَحِيَّتُكَ وَتَحِيَّةُ ذُرِّيَّتكَ، فَذَهَبَ فقال: السَّلَامُ عَلَيْكُمْ، فَقَالُوا: السَّلَامُ عَلَيْكَ وَرحْمةُ اللَّه، فَزَادُوهُ: وَرَحْمةُ اللَّه. فَكُلُّ مَنْ يَدْخُلُ الْجَنَّةَ عَلَى صُورِةَ آدَمَ فِى طُولِهِ ستُّونَ ذِرَاعًا، فَلَم يَزَل الْخَلْقُ يَنْقُصُ بَعْدُ حَتَّى الآن".