I’tikaaf is prescribed in Islam and it is an act of worship that draws one closer to Allaah. See Question no. (48999)
Once this is established, there are many ahaadeeth which encourage us to draw closer to Allaah by doing naafil acts of worship. The general meaning of these ahaadeeth includes all kinds of worship, including i’tikaaf.
For example, there is the hadeeth qudsi in which Allaah 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-Bukhaari, 6502.
There are several ahaadeeth which speak of the virtue of i’tikaaf and describe its reward, but they are all weak (da’eef) or fabricated (mawdoo’).
Abu Dawood said: I said to Ahmad (i.e., Imam Ahmad ibn Hanbal): Do you know anything about the virtue of i’tikaaf? He said: No, except something weak. Masaa’il Abi Dawood, p. 96.
These ahaadeeth include the following:
1 – Ibn Maajah (1781) narrated from Ibn ‘Abbaas that the Messenger of Allaah (peace and blessings of Allaah be upon him) said concerning the person who observes i’tikaaf: “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’eef by al-Albaani in Da’eef Ibn Maajah.
2 – al-Tabaraani, al-Haakim and al-Bayhaqi narrated the following from Ibn ‘Abbaas, which they classed as da’eef: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever observes i’tikaaf for one day seeking thereby the Face of Allaah, Allaah will place between him and the Fire three ditches wider than the distance between the east and the west.” This was classed as da’eef by al-Albaani in al-Silsilah al-Da’eefah, 5345.
3 – al-Daylami narrated from ‘Aa’ishah that the Prophet (peace and blessings of Allaah be upon him) said: “Whoever observes i’tikaaf out of faith and in the hope of reward will be forgiven his previous sins.” Classed as da’eef by al-Albaani in Da’eef al-Jaami’, 5442.
4 – Al-Bayhaqi narrated the following report from al-Husayn ibn ‘Ali (may Allaah be pleased with him), which he classed as da’eef: the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever observes i’tikaaf for ten days in Ramadaan, that will be equivalent to two Hajjs and two ‘Umrahs. This was mentioned by al-Albaani in al-Silsilah al-Da’eefah (518) where he said: it is mawdoo’ (fabricated).