The people (mostly) were workers and they would come for Friday prayer in the same condition, so it was said to them: If only you were to perform Ghusl.  

كَانَ النَّاسُ مُهَّانَ أَنْفُسِهِمْ فَيَرُوحُونَ إِلَى الْجُمُعَةِ بِهَيْئَتِهِمْ فَقِيلَ لَهُمْ لَوِ اغْتَسَلْتُمْ  

Some people of Iraq came and said: Ibn 'Abbas, do you regard taking a bath on Friday as obligatory ? He said: No, it is only a means of cleanliness, and is better for one who washes oneself. Anyone who does not take a bath, it is not essential for him. I inform you how the bath (on Friday) commenced. The people were poor and used to wear woolen clothes, and would carry loads on their backs. Their mosque was small and its rood was lowered down. It was a sort of trellis of vine. The Messenger of Allah ﷺ once came out on a hot day and the people perspired profusely in the woolen clothes so much so that foul smell emitted from them and it caused trouble to each other. When the Messenger of Allah ﷺ found the foul smell, he said: O people, when this day (Friday) comes, you should take bath and every one should anoint the best oil and perfume one has. Ibn 'Abbas then said: Then Allah, the Exalted, provided wealth (to the people) and they wore clothes other than the woolen, and were spared from work, and their mosque became vast. The foul smell that caused trouble to them became non-existent.  

لاَ وَلَكِنَّهُ أَطْهَرُ وَخَيْرٌ لِمَنِ اغْتَسَلَ وَمَنْ لَمْ يَغْتَسِلْ فَلَيْسَ عَلَيْهِ بِوَاجِبٍ وَسَأُخْبِرُكُمْ كَيْفَ بَدْءُ الْغُسْلِ كَانَ النَّاسُ مَجْهُودِينَ يَلْبَسُونَ الصُّوفَ وَيَعْمَلُونَ عَلَى ظُهُورِهِمْ وَكَانَ مَسْجِدُهُمْ ضَيِّقًا مُقَارِبَ السَّقْفِ إِنَّمَا هُوَ عَرِيشٌ فَخَرَجَ رَسُولُ اللَّهِ ﷺ فِي يَوْمٍ حَارٍّ وَعَرِقَ النَّاسُ فِي ذَلِكَ الصُّوفِ حَتَّى ثَارَتْ مِنْهُمْ رِيَاحٌ آذَى بِذَلِكَ بَعْضُهُمْ بَعْضًا فَلَمَّا وَجَدَ رَسُولُ اللَّهِ ﷺ تِلْكَ الرِّيحَ قَالَ أَيُّهَا النَّاسُ إِذَا كَانَ هَذَا الْيَوْمُ فَاغْتَسِلُوا وَلْيَمَسَّ أَحَدُكُمْ أَفْضَلَ مَا يَجِدُ مِنْ دُهْنِهِ وَطِيبِهِ قَالَ ابْنُ عَبَّاسٍ ثُمَّ جَاءَ اللَّهُ بِالْخَيْرِ وَلَبِسُوا غَيْرَ الصُّوفِ وَكُفُوا الْعَمَلَ وَوُسِّعَ مَسْجِدُهُمْ وَذَهَبَ بَعْضُ الَّذِي كَانَ يُؤْذِي بَعْضُهُمْ بَعْضًا مِنَ الْعَرَقِ  

If any one of you performs ablution (on Friday) that is all right; and if any of you takes a bath, that is better.  

قَالَ رَسُولُ اللَّهِ ﷺ مَنْ تَوَضَّأَ يَوْمَ الْجُمُعَةِ فَبِهَا وَنِعْمَتْ وَمَنِ اغْتَسَلَ فَهُوَ أَفْضَلُ