Assalamualaikum ustaz. Can you explain the ruling of isbal for men?
Waalaikumussalam wrt. wbt.,
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions, and all those who follow his footsteps until the Final day.
Basically, Allah SWT commanded His slaves to wear aurah covering clothes. This is based on the Quranic evidence:
يَا بَنِي آدَمَ قَدْ أَنزَلْنَا عَلَيْكُمْ لِبَاسًا يُوَارِي سَوْآتِكُمْ وَرِيشًا ۖ وَلِبَاسُ التَّقْوَىٰ ذَٰلِكَ خَيْرٌ ۚ
“O children of Adam, We have bestowed upon you clothing to conceal your private parts and as adornment. But the clothing of righteousness – that is best.”
According to the above verse, there are three types of clothing mentioned by Allah SWT which are the clothing that covers the aurah, clothing as an adornment and the clothing of taqwa. The word “اللباس” in the verse refers to the basic clothing (dharuriyah) to cover the aurah. While “الريش” is something that is worn to look beautiful on the outside (takmilat). Whereas, the clothing of taqwa is meant through majazi (figuratively) as good deeds according to Ibnu Abbas. 
Furthermore, Islam prohibits its ummah from becoming wasteful or boastful according to the statement of Allah SWT:
يَا بَنِي آدَمَ خُذُوا زِينَتَكُمْ عِندَ كُلِّ مَسْجِدٍ وَكُلُوا وَاشْرَبُوا وَلَا تُسْرِفُوا ۚ إِنَّهُ لَا يُحِبُّ الْمُسْرِفِينَ
“O children of Adam, take your adornment at every masjid, and eat and drink, but be not excessive. Indeed, He likes not those who commit excess.” 
The above verse shows that every human being should be modest in doing anything, for Allah dislike those who transgress.  This verse also explains that Allah SWT dislikes those who are wasteful or excessive in food, drink and all other aspects. 
Moreover, every Muslim should distance himself from matters that can cause boastfulness and vanity. Allah SWT states:
وَاللَّـهُ لَا يُحِبُّ كُلَّ مُخْتَالٍ فَخُورٍ
“And Allah does not like everyone self-deluded and boastful.” 
The Ruling of Isbal for Men
Coming back to the above question, Iqbal lexically a masdar from ‘أَسْبَلَ، يُسبل، إسبالاً’, which means ‘الإرخاء’ which means lengthening, extending, elongating. While the terminology means as stated by Ibn al-‘Arabi and others said lengthening, extending and elongating the clothing over the ankles and touching the soil, whether it is due to boastfulness or otherwise. 
In the fiqh discussion, the word “isbal” can refer to various meanings. Some scholars refer to this terminology as the act of releasing one’s hands during the recitation of al-Fatihah in prayer. This is the opinion held by some scholars in madhhab Maliki which is different from the qaul of jumhur which places the sunnah ruling of placing the right hand on the left hand.
Isbal also as explained usually refers to the act of a person lengthening his clothing such as jubah or trousers passing his ankles. This act isn’t an issue but encouraged for women to cover their aurah, but for men, scholars have differing opinions.
From Abu Dzar RA, Rasullullah PBUH said:
ثَلَاثَةٌ لَا يُكَلِّمُهُمُ اللهُ يَوْمَ الْقِيَامَةِ، وَلَا يَنْظُرُ إِلَيْهِمْ وَلَا يُزَكِّيهِمْ وَلَهُمْ عَذَابٌ أَلِيمٌ» قَالَ: فَقَرَأَهَا رَسُولُ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ ثَلَاثَ مِرَارًا، قَالَ أَبُو ذَرٍّ: خَابُوا وَخَسِرُوا، مَنْ هُمْ يَا رَسُولَ اللهِ؟ قَالَ: «الْمُسْبِلُ، وَالْمَنَّانُ، وَالْمُنَفِّقُ سِلْعَتَهُ بِالْحَلِفِ الْكَاذِبِ
“There are three to whom God will not speak on the day of resurrection, at whom He will not look, and whom He will not declare pure, and they will have a painful punishment.” Abu Dharr said, “They are losers and disappointed. Who are they, Messenger of God?” He replied, “The one who wears a trailing robe, the one who takes account of what he gives*, and the one who produces a ready sale of a commodity by false swearing.” 
Some scholars stated that the reason for the prohibition of isbal is because this action refers to the customs of jahiliyyah for the nobles who lengthen their clothing that it trails behind them and is lifted by their slaves. This characteristic symbolizes boastfulness and showing off of their wealth. This characteristic also denied the attribute of humility.
This is in line with the statement of Allah SWT:
وَلَا تَمْشِ فِي الْأَرْضِ مَرَحًا ۖ إِنَّكَ لَن تَخْرِقَ الْأَرْضَ وَلَن تَبْلُغَ الْجِبَالَ طُولًا
“And do not walk upon the earth exultantly. Indeed, you will never tear the earth [apart], and you will never reach the mountains in height.” 
It should be analyzed that this prohibition shows to a ta’abbudi prohibition or mahdhah or in worldly matters which are bound with ilah.
Syeikh Dr Yusuf al-Qaradhawi explained this matter in his book Kaifa Nata’amal Ma’a al-Sunnah al-Nabawiyyah (pg. 125), by citing another hadith from Abdullah bin Umar R.Anhuma, where Rasullullah PBUH said:
مَنْ جَرَّ ثَوْبَهُ خُيَلاَءَ، لَمْ يَنْظُرِ اللَّهُ إِلَيْهِ يَوْمَ القِيَامَةِ» فَقَالَ أَبُو بَكْرٍ: إِنَّ أَحَدَ شِقَّيْ ثَوْبِي يَسْتَرْخِي، إِلَّا أَنْ أَتَعَاهَدَ ذَلِكَ مِنْهُ؟ فَقَالَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ: إِنَّكَ لَسْتَ تَصْنَعُ ذَلِكَ خُيَلاَءَ
“Allah will not look on the Day of Judgment at him who drags his robe (behind him) out of pride.” Abu Bakr said, “One side of my robe slacks down unless I get very cautious about it.” Allah’s Messenger (ﷺ) said, “But you do not do that with a pride.“ 
Syeikh Dr Yusuf al-Qaradhawi also stated the conclusion drawn by Imam Nawawi and Imam Ibn Hajar al-Asqalani the prohibition of isbal is related to the attribute of (خيلاء) which means boastfulness.
Thus, after considering the related evidences, the conclusion drawn is, if it is the custom of a person and the society to do isbal without the purpose of boastfulness and showing off, then it is exempted from the prohibition in the hadith.