The ornament of the believer will reach as far as his ablution reaches
Authentic hadithعن أبي هريرة رضي الله عنه قال قال رسول الله صلى الله عليه وسلم : ((إن أمتي يُدْعَون يوم القيامة غُرًّا مُحَجَلِّين من آثار الوُضُوء)). فمن اسْتَطَاع منكم أن يُطِيل غُرَّتَه فَليَفعل. وفي لفظ لمسلم: ((رأَيت أبا هريرة يتوضَّأ، فغسل وجهه ويديه حتى كاد يبلغ المنكبين، ثم غسل رجليه حتى رَفَع إلى السَّاقين، ثم قال: سمعت رسول الله صلى الله عليه وسلم يقول: إنَّ أمتي يُدْعَون يوم القيامة غُرًّا مُحَجَّلِين من آثار الوُضُوء)) فمن استطاع منكم أن يطيل غُرَّتَه وتَحْجِيلَه فَليَفعَل. وفي لفظ لمسلم: سمعت خليلي صلى الله عليه وسلم يقول: ((تَبْلُغ الحِليَة من المؤمن حيث يبلغ الوُضُوء)).
Abu Hurayrah (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) said: "My followers will be called on the Day of Resurrection with radiant foreheads and feet from the traces of ablution." So whoever can increase the area of his radiance should do so. And in a wording by Muslim: "I saw Abu Hurayrah performing ablution. He washed his face, then his arms until he almost reached the shoulders, and then he washed his feet up to the shins, and said: ‘I heard the Messenger of Allah (may Allah's peace and blessings be upon him) say: 'My followers will be called on the Day of Resurrection with radiant foreheads and feet from the traces of ablution.' So whoever can increase the area of his radiance should do so.'" And in another wording by Muslim: "I heard my close friend (may Allah's peace and blessings be upon him) say: ‘The adornment of the believer will reach as far as his ablution reaches.'"
Explanation
The Prophet (may Allah's peace and blessings be upon him) gives his followers the glad tidings that Allah, Glorified and Exalted, will grant them a sign of virtue and honor on the Day of Resurrection that will distinguish them from other nations. When called out, they will emerge, distinct from the rest of people with their radiant faces, hands and feet. This light is from the traces of a great act of worship, i.e. ablution, which they often performed on their limbs. In that they sought Allah's pleasure and reward, hence they will have admirable reward of illumination. Abu Hurayrah recommended to extend this radiance, because washing more space of the body yields more radiance. Indeed, the ornamentation of light reaches as far as the water of ablution reaches. However, in mandatory ablution, one washes the hands up to the elbow and a little bit further, and washes the feet up to the ankles and a little bit further. It is not required to wash the upper arms and shins.
Source · Muslim with its two versions - Narrated by Bukhari & Muslim
From the Hadith Encyclopedia (hadeethenc.com).