Virtues of Du’a on the Day of ‘Arafah
Question

Will du’a offered on the day of ‘Arafah by those who are not on Hajj be answered?
Praise be to Allah.Best Du`a on the Day of Arafah
‘Aishah (may Allah be pleased with her) said: The Messenger of Allah (peace and blessings of Allah be upon him) said: “There is no day on which Allah ransoms more of His slaves from the Fire than the day of ‘Arafah . He draws close then He boasts about them before the angels and says, ‘What do these people want?’” (Narrated by Muslim, 1348) 
 ‘Abd-Allah ibn ‘Amr ibn al-‘As (may Allah be pleased with him) narrated that the Prophet (peace and blessings of Allah be upon him) said: “The best of du’a is du’a on the day of ‘Arafah, and the best that I and the Prophets before me said is ‘La ilaha ill-Allah wahdahu la sharika lah, lahu’l-mulk wa lahu’l-hamd wa huwa ‘ala kulli shay’in qadir (There is no god but Allah Alone, with no partner or associate; His is the dominion, to Him be praise, and He has power over all things).” (Narrated by al-Tirmidhi (3585)’ classed as hasan by al-Albani in Sahih al-Targhib (1536)
Talhah ibn ‘Ubayd ibn Kurayz narrated in a mursal report: “The best of du’a is du’a on the day of ‘Arafah.” (Narrated by Malik in al-Muwatta’ (500); classed as hasan by al-Albani in Sahih al-Jami’ (1102) 
Virtues of Du`a on the Day of Arafah: For Pilgrim Only?
The scholars differed concerning this virtue of du’a on the day of ‘Arafah , whether it applies only to those who are in ‘Arafah or it includes other places. The more correct view is that it is general and that the virtue is connected to the day, but undoubtedly those who are in ‘Arafah have combined the virtue of the place with the virtue of the time. 
Al-Baji (may Allah have mercy on him) said: 
“The words “The best of du’a is on the day of ‘Arafah ” mean the dhikr with the greatest blessing, the greatest reward and that which is most likely to be answered. It may be interpreted as referring to pilgrims only, because the meaning of du’a on the day of ‘Arafah is very true in their case, and applies especially to them. But if the day of ‘Arafah is regarded in general terms, it is described as such because of the pilgrims being there. And Allah knows best.” (Al-Muntaqa Sharh al-Muwatta, 1/358) 
It is proven that some of the salaf regarded “al-ta’rif” as permissible, which means gathering in the mosques to offer du’a and remember Allah (dhikr) on the day of ‘Arafah . Among those who did that was Ibn 'Abbas (may Allah be pleased with him). Imam Ahmad also regarded it as permissible although he did not do it himself. 
Ibn Qudamah (may Allah have mercy on him) said: 
“Al-Qadi said: There is nothing wrong with ta’rif, gathering in the afternoon of the day of ‘Arafah in the regions (i.e., other than ‘Arafah). Al-Athram said: I asked Abu ‘Abd-Allah (i.e., Imam Ahmad) about ta’rif in the regions, where they gather in the mosques on the day of ‘Arafah, and he said: I hope that there is nothing wrong with it, as more than one did it. Al-Athram narrated that al-Hasan said: The first one who did ta’rif in Basra was Ibn 'Abbas (may Allah have mercy on him). Ahmad said: The first ones who did it were Ibn 'Abbas and ‘Amr ibn Hurayth. 
Al-Hasan, Bakr, Thabit and Muhammad ibn Wasi’ used to attend the mosque on the day of ‘Arafah. Ahmad said: There is nothing wrong with it, it is only du’a and remembrance of Allah (dhikr). It was said to him: Do you do it? He said: As for me, no. And it was narrated that Yahya ibn Ma’in attended (the mosque) with the people on the afternoon of ‘Arafah.” (Al-Mughni, 2/129) 
This indicates that they thought that the virtue of the day of ‘Arafah did not apply only to the pilgrims, although gathering to remember Allah and say du’a in the mosques on the day of ‘Arafah was not narrated from the Prophet (peace and blessings of Allah be upon him). Hence Imam Ahmad did not do it, but he allowed it and did not forbid it, because it was narrated that some of the Sahabah did it, such as Ibn 'Abbas and ‘Amr ibn Hurayth (may Allah be pleased with them). 
And Allah knows best.