Al-Haafidh Ibn Rajab (rahimahullaah) mentioned:

Hakeem bin Hizaam (radhiyallaahu anhu) would stand at Arafah and with him would be one hundred camels, and one hundred slaves, so he would free his slaves. So the people would become boisterous with weeping and supplicating saying: "Our Lord; this is your slave who has freed his slaves; and we are your slaves so liberate us [from The Fire]."

It is reported from Ibn Umar (radhiyallaahu anhumaa) that he stood at Arafah, so he would raise his hands - or (the narrator said) that he would put his hands out - and I do not know perhaps he said that they were positioned lower than his ears and he would say: "Allaahu Akbar wa lillaahil hamd; Allaahu Akbar wa lillaahil hamd; Allaahu Akbar wa lillaahil hamd; wa laa ilaaha illallaahu wahdahu laa shareekalahu; lahul Mulku wa lahul hamdu; Allaahummahdini bil hudaa; wa naqqinee bit-taqwaa waghfir lee fil aakhirati wal oolaa." Then he would bring his hands back and be silent for the duration that it would take a person to recite Surah al-Faatihah. Then he would return, so he would raise his hands and say the like of that.

Umar bin Abdil-Azeez gave a sermon at Arafah and said: Indeed, you have come from near and far, and have exhausted the backs and have worn out the garments. And the one who precedes today isn't the one whose riding beast and riding camel precedes; rather the one who precedes today is the one who is forgiven."

It is reported that Sufyaan At-Thawree stood at Arafah and whilst there he saw a people from those well-known who committed major sins and wickedness. So it transpired upon his heart: "Do you see that these people will be forgiven?" So he slept and in his sleep it was said to him: "O Abaa Abdillaah; We have pardoned much more than their sins, indeed We have forgiven them all."

Ahkaam 'Arafah p.199-204 & Lataa'if wal Ma'aarif p.382-385
Translated by Abu Haatim Muhammad