Is Arabic the language of the people of Paradise?
Question

                I would like to know what the language of the people of Paradise is. Is it Arabic?.
Praise be to Allah.There is no 
    mention in the Qur’aan or in the saheeh Sunnah – as far as we know – of 
    which language is spoken by the people of Paradise. What is narrated 
    concerning that is a hadeeth which is not soundly narrated from our Prophet 
     (peace and blessings of Allaah be upon him), and some other reports 
    (athaar). 
It was 
    narrated by al-Tabaraani in al-Awsat, al-Haakim, al-Bayhaqi in 
    Shu’ab al-Eemaan and others that Ibn ‘Abbaas (may Allaah be pleased with 
    him) said: The Messenger of Allaah  (peace and blessings of Allaah be 
    upon him) said: “Love the Arabs for three reasons, because I am an Arab, the 
    Qur’aan is Arabic and the speech of the people of Paradise is Arabic.”
 Ibn 
    al-Jawzi ruled that this hadeeth is fabricated. Al-Dhahabi said: I think 
    that the hadeeth is fabricated (mawdoo’). Al-Albaani said in al-Silsilah 
    al-Da’eefah (no. 160): (it is) fabricated. 
Shaykh 
    al-Islam Ibn Taymiyah (may Allaah have mercy on him) said: Similarly, Abu 
    Ja’far Muhammad ibn ‘Abd-Allaah al-Haafiz al-Koofi, who is known as Mateen, 
    told us: al-‘Ala’ ibn ‘Amr al-Hanafi told us: Yahya ibn Zayd al-Ash’ari told 
    us: Ibn Jurayj told us, from Ibn 'Abbaas (may Allaah be pleased with him) 
    that he said: the Messenger of Allaah  (peace and blessings of Allaah be 
    upon him) said: “Love the Arabs for three reasons: because I am an Arab, the 
    Qur’aan is Arabic, and the language of the people of Paradise is Arabic.” 
Al-Haafiz 
    al-Salafi said: this is a hasan hadeeth. I do not know whether he meant that 
    its isnaad is hasan according to the way of the scholars of hadeeth, or that 
    its text is hasan in general terms. Abu’l-Faraj ibn al-Jawzi mentioned this 
    hadeeth among the mawdoo’ (fabricated) texts and said: al-Tha’labi said: it 
    has no basis. Ibn Hibbaan said: Yahya ibn Zayd narrated unsound ahaadeeth 
    from sound narrators, so it is invalid to quote his reports as evidence. And 
    Allaah knows best. 
End quote 
    from Iqtida’ al-Siraat al-Mustaqeem (1/158). 
Al-Tabaraani 
    narrated in al-Awsat that Abu Hurayrah (may Allaah be pleased with 
    him) said: the Messenger of Allaah  (peace and blessings of Allaah be 
    upon him) said: “I am an Arab, and the Qur’aan is Arabic, and the language 
    of the people of Paradise is Arabic.” 
Al-Albaani 
    said in al-Silsilah al-Da’eefah (no. 161): it is fabricated. 
The point is 
    that there is no saheeh evidence to show which language is spoken by the 
    people of Paradise. Hence we should refrain from speaking about this issue 
    and not indulge in it, and we should refer knowledge of the matter to Allaah 
    (may He be exalted), and focus instead on issues that will lead to good 
    deeds in this world. 
Shaykh 
    al-Islam Ibn Taymiyah (may Allaah have mercy on him) was asked: in what 
    (language) will Allaah address the people on the Day of Resurrection? Will 
    Allaah address them in the tongue of the Arabs? Is it true that the language 
    of the people of Hell will be Farsi and that the language of the people of 
    Paradise will be Arabic? He replied: Praise be to Allaah, the Lord of the 
    Worlds. It is not known what language the people will speak on that Day, or 
    in what language they will hear the words of the Lord, may He be exalted, 
    because Allaah has not told us anything about that, nor has His Messenger 
     (peace and blessings of Allaah be upon him). It is not true that Farsi 
    will be the language of the people of Hell, or that Arabic will be the 
    language of the people of Paradise. We do not know of any discussion of that 
    among the Sahaabah (may Allaah be pleased with them), rather all of them 
    refrained from speaking of that because speaking about such a thing is 
    discussion of something unnecessary… but there was a dispute concerning that 
    among later scholars. Some people said that they will be addressed in Arabic 
    and others said that the people of Hell will respond in Farsi, which will be 
    their language in Hell. Others said that they will be addressed in Syriac 
    because that was the language of Adam and from it stemmed all other 
    languages. Others said that the people of Paradise will speak Arabic. There 
    is no basis for any of these ideas, whether on the grounds of common sense 
    or in any report or text, rather they are mere claims that are devoid of any 
    evidence. And Allaah knows best and is most Wise. End quote. 
Majmoo’ 
    al-Fataawa (4/299) 
And Allaah 
    knows best.