Fasting on the Day of Arafah
Question

We have a Shaykh who says that fasting on the day of ‘Arafah is not Sunnah, and it is not permissible to fast on this day. I hope that you can answer this question, because this Shaykh distributes pamphlets which tell people not to fast on the day of ‘Arafah.
Praise be to Allah.Fasting on the day of ‘Arafah is a confirmed Sunnah for those who are not performing Hajj. 
Abu Qatadah (may Allah be pleased with him) narrated that the Messenger of Allah (peace and blessings of Allah be upon him) was asked about fasting on the day of ‘Arafah and he said: “It expiates for the past and coming years.” Narrated by Muslim (1162). According to another report: “I ask Allah that it may expiate for (the sins of) the year that comes before it and the year that comes after it.” 
Al-Nawawi (may Allah have mercy on him) said in al-Majmu’ (6/428), which is a Shafi'i book: 
“With regard to the ruling on this matter, al-Shafi'i and his companions said: It is mustahabb to fast on the day of ‘Arafah for the one who is not in ‘Arafah. As for the pilgrim who is present in ‘Arafah, al-Shafi'i said in al-Mukhtasar and his companions said: It is mustahabb for him not to fast, because of the hadith of Umm al-Fadl. A number of our companions said: It is makruh for him to fast this day. Among those who stated that it is makruh were al-Darimi, al-Bandaniji, al-Muhamili in al-Majmu’ and al-Musannaf fi’l-Tanbih, and others.”
Ibn Qudamah (may Allah have mercy on him) said in al-Mughni (4/443), which is a Hanbali book: 
“It is a great and noble day, and a blessed festival which is of great virtue. It is narrated in sahih reports from the Prophet (peace and blessings of Allah be upon him) that fasting it is expiation for two years.”
Ibn Muflih (may Allah have mercy on him) said in al-Furoo’ (3/108), which is also a Hanbali book: 
“It is mustahabb to fast the first nine days of Dhu’l-Hijjah, especially the ninth day, which is the day of ‘Arafah, according to scholarly consensus.”
Al-Kasani (may Allah have mercy on him) said in Badai' al-Sanai’ (2/76), which is a Hanafi book: 
“With regard to fasting the day of ‘Arafah, for people other than those who are performing Hajj it is mustahabb, because of the many ahadith which recommended fasting on this day, and because it is superior to other days. That also applies to the pilgrim if it will not make him too weak to stand in ‘Arafah and say du’a, because this is combining two acts of worship. But if it will make him too weak, then it is makruh, because the virtue of fasting on this day is something that may be made up in some other year, whereas the virtue of standing in ‘Arafah and making du’a is something that is not attainable for most people, except once in a lifetime, therefore attaining that virtue (of standing in ‘Arafah and making du’a) takes precedence.”  
In Sharh Mukhtasar Khalil, by al-Khurashi (6/499), which is a Maliki book, it says: 
“Fasting on the day of ‘Arafah, for one who is not doing Hajj, and the ten days of Dhu’l-Hijjah, ''what is meant is that fasting on the day of ‘Arafah is mustahabb for the one who is not doing Hajj. As for the pilgrim, it is mustahabb for him not to fast this day, so as to strengthen himself for supplicating (du’a), and the Prophet (peace and blessings of Allah be upon him) did not fast during Hajj.”
In Hashiyat al-Dusuqi (5/80) it says: 
“It is recommended to fast on the day of ‘Arafah …”, what is meant is that it is particularly recommended on this day, otherwise fasting is recommended in general.”  
Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) was asked: What is the ruling on fasting on the day of ‘Arafah for non-pilgrims and pilgrims?  
He replied: 
“Fasting on the day of ‘Arafah for non-pilgrims is a confirmed Sunnah. The Messenger of Allah (peace and blessings of Allah be upon him) was asked about fasting on the day of ‘Arafah and he said: “I ask Allah that it may expiate for (the sins of) the year that comes before it and the year that comes after it.” According to another report he said: “It expiates for the past and coming years.” 
As for the pilgrim, it is not Sunnah for him to fast on the day of ‘Arafah, because the Prophet (peace and blessings of Allah be upon him) did not fast on the day of ‘Arafah during the Farewell Pilgrimage. In Sahih al-Bukhari it is narrated from Maymunah (may Allah be pleased with her) that the people were not sure whether the Prophet (peace and blessings of Allah be upon him) was fasting on the day of ‘Arafah, so she sent him some milk when he was standing in ‘Arafah, and he drank it whilst the people were looking on.” (Majmu’ Fatawa Ibn ‘Uthaymin, part 20, question no. 404) 
Fasting on the day of ‘Arafah is makruh for the pilgrim and not mustahabb. If this is what the speaker meant, then he is correct. But if what he meant is that it is not prescribed to fast on the day of ‘Arafah for non-pilgrims, then this is a mistake which clearly goes against the sahih Sunnah, as stated above.
For more about the rulings related to ‘Arafah, please see these answers: 128256 , 70282 , 136192 , 109311 ,  and 106483 .
And Allah knows best.