Virtues of I’tikaf
Question

What is the reward for i’tikaaf?
Praise be to Allah.Virtues of i’tikaf
I’tikaf is prescribed in Islam and it is an act of worship that draws one closer to Allah. 
Once this is established, there are many ahadith which encourage us to draw closer to Allah by doing nafl acts of worship . The general meaning of these ahadith includes all kinds of worship, including i’tikaf . 
For example, there is the hadith qudsi in which Allah says: “My servant draws not near to Me with anything more loved by Me than the religious duties I have enjoined upon him, and My servant continues to draw near to Me with supererogatory works so that I shall love him. When I love him I am his hearing with which he hears, his seeing with which he sees, his hand with which he strikes and his foot with which he walks. Were he to ask [something] of Me, I would surely give it to him, and were he to ask Me for refuge, I would surely grant him it.” (Narrated by al-Bukhari, 6502) 
Weak hadiths on the virtues of i’tikaf
There are several ahadith which speak of the virtue of i'tikaf and describe its reward, but they are all weak (da’if) or fabricated (mawdu’). 
Abu Dawud said: I said to Ahmad (i.e., Imam Ahmad ibn Hanbal): Do you know anything about the virtue of i’tikaf? He said: No, except something weak. Masail Abi Dawud, p. 96. 
These ahadith include the following: 

Ibn Majah (1781) narrated from Ibn 'Abbas that the Messenger of Allah (peace and blessings of Allah be upon him) said concerning the person who observes i’tikaf: “He is refraining from sin and he will be given a reward like that of one who does all kinds of good deeds.”  This was classed as da’if by al-Albani in Da’if Ibn Majah. 
Al-Tabarani, al-Hakim and al-Bayhaqi narrated the following from Ibn 'Abbas, which they classed as da’if: The Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever observes i’tikaf for one day seeking thereby the Face of Allah, Allah will place between him and the Fire three ditches wider than the distance between the east and the west.” This was classed as da’if by al-Albani in al-Silsilah al-Da’ifah, 5345.  
Al-Daylami narrated from ‘Aishah that the Prophet (peace and blessings of Allah be upon him) said: “Whoever observes i’tikaf out of faith and in the hope of reward will be forgiven his previous sins.” Classed as da’if by al-Albani in Da’if al-Jami’, 5442. 
Al-Bayhaqi narrated the following report from al-Husayn ibn ‘Ali (may Allah be pleased with him), which he classed as da’if: the Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever observes i'tikaf for ten days in Ramadan, that will be equivalent to two Hajjs and two ‘Umrahs. This was mentioned by al-Albani in al-Silsilah al-Da’ifah (518) where he said: it is mawdu’ (fabricated).

And Allah knows best.