Shaykh Muhammad bin Saalih al-Uthaymeen rahimahullaah said:
Hajj has tremendous virtue and many great benefits:
(1) From them is His saying – He the Most High –:
لِّيَشْهَدُوا مَنَافِعَ لَهُمْ وَيَذْكُرُوا اسْمَ اللَّهِ فِي أَيَّامٍ مَّعْلُومَاتٍ عَلَىٰ مَا رَزَقَهُم مِّن بَهِيمَةِ الْأَنْعَامِ
[[Meaning: That they may witness things that are of benefit to them and mention the name of Allah on known days over what He has provided for them of sacrificial animals.]]
So in it – in addition to the fact it being an act of worship, and remembrance of Allaah the Mighty and Majestic – are things that are of benefit to the people.
(2) And from the benefits is people getting to know each other. I – for example – here in the Kingdom of Saudi Arabia, meet with people who have come from east Asia, and with people who have come from the farthest parts of Africa, and even further than that; and I do not know them and they do not know me previous to that.
And generally people getting to know each other results in their affinity. Meaning: the unification of their hearts, and the people having love for one another.
(3) And from them the benefits is trade; and trade has a great importance. Do the pilgrims import or export wealth? [The answer is] both – they export it and import it; they come with items and they leave with items. So there is benefit from both sides.
(4) And from the benefits is that which the poor people benefit from by way of what they receive in charity, and by way of the kindness the rich show to them, and by way of the sacrificing of the sacrificial animals.
(5) And from the benefits is being reminded of the Day of Resurrection – because of the people all wearing the same clothing, having the same appearance, and carrying out the same actions.
(6) And from the benefits is being reminded of the Day of Resurrection due to their passage in hordes; everyone going to their destination. And if you were to stop on the path on the day of `Arafah (9th of Dhul-Hijjah) and see the people you would be reminded of the gathering [when Allaah resurrects the people from their graves].
See: ‘Fathu Dhil-Jalaali wal-Ikraam’ of Shaykh ibn `Uthaymeen rahimahullaah; vol. 8, pp. 9-10.