Salah (Prayer) inside the Ka’bah (Hijr) is preferred and is a means of drawing close (to Allaah)
Making Takbir, then du’aa to Allaah after praying two rak’ah inside the Ka’bah (Hijr) is a Sunnah
Question: Is salat inside the Ka’bah in any way superior to salat outside it, and is it permissible for a person to speak of what he has seen inside the ka’bah?
Answer by The Permanent Committee: Salat inside the Ka’bah is preferred, if it is possible to do so without any inconvenience, difficulty or harm to anyone, as the Prophet (salallaahu ‘alaihi wa sallam) entered it and prayed therein, according to an authentic narration in the Sahihain (Two Sahihs). And it has been reported from him (salallaahu ‘alaihi wa sallam) that he came out one day looking sad, and he said: “Verily, I fear that I may have placed a burden upon my Ummah (i.e. by entering the ka’bah).” 
And when ‘A`ishah (radiallaahu ‘anha) asked him about salat in the Ka’bah, he said: “Pray in the Hijr, because it is a part of the House.” 
This proves that salat inside the Ka’bah is preferred and is a means of drawing close (to Allaah) and an act of obedience, and in it is great merit.
However, it is not fitting that there should be crowding, or harm, or doing anything which causes difficulty to him or to the people. It is enough for him to pray in the Hijr, because it is a part of the House; and there is no objection to speaking about what he has seen inside the Ka’bah, such as its inscriptions, or what is on its ceiling or the like. There is no objection to a person talking and saying: “I saw such and such and such and such.” There is no sin in that.
The Sunnah, when one enters the Ka’bah, is to pray two rak’ahs and to say “Allaahu Akbar” and invoke Allaah, the Almighty, the All-Powerful with whatever supplications are easy for him at the end of it, especially those which have been reported (from the Prophet, salallaahu ‘alaihi wa sallam) because the Prophet (salallaahu ‘alaihi wa sallam) entered the Ka’bah and prayed therein, then he performed Takbir and supplicated Allaah. All of this has been authentically reported from him (salallaahu ‘alaihi wa sallam).
The Permanent Committee; Fatawa Islamiya, Volume 2
 Abu Dawud no. 2029.
 Abu Dawud no. 2028; Ahmad 6:92