I just recently found out about this and am confused on whether it is sunnah or wajib.
If it is wajib, will all my past salah count?
Also, is it wajib or sunnah to say takbeer when changing postures in salah (i.e. qiyam to ruku, ruku to sujood etc...)
Praise be to Allah.
The scholars differed concerning the ruling on the takbeers of movement in the prayer and on saying between the two prostrations, “Rabb ighfir li (Lord forgive me).” There are two opinions:
The first opinion, which is the view of the majority of Hanafis, Maalikis and Shaafa‘is, is that the takbeers of movement and saying “Rabb ighfir li (Lord forgive me)” between the two prostrations come under the heading of the Sunnahs of prayer and are not obligatory parts of the prayer.
The second opinion is that they are obligatory parts of the prayer. This is the view of the Hanbalis.
Ibn Qudaamah (may Allah have mercy on him) said in al-Mughni (1/298): The well known view narrated from Ahmad is that the takbeer said when going down and coming up, the tasbeehs of bowing and prostration, saying “Sami‘ Allahu liman hamidah, Rabbana wa laka al-hamd (Allah hears those who praise Him, our Lord to You be praise)”, saying “Rabb ighfir li (Lord forgive me)”, saying “Rabb ighfir li (Lord forgive me)” between the two prostrations, and the first tashahhud, are all obligatory. It is also the view of Ishaaq and Dawood.
And it was narrated from Ahmad that it is not obligatory, which is the view of most of the fuqaha’, because the Prophet (blessings and peace of Allah be upon him) did not teach it to the one who prayed improperly, and it is not permissible to delay explaining something at the time when it becomes necessary. Moreover, Ibn Qudaamah quoted a number of things to indicate that it is obligatory:
1. The Prophet (blessings and peace of Allah be upon him) enjoined it, and his instruction indicates that something is obligatory.
2. He did it and he said: “Pray as you have seen me praying.”
3. Abu Dawood (856) narrated from ‘Ali ibn Yahya ibn Khallaad from his paternal uncle that the Prophet (blessings and peace of Allah be upon him) said: “The prayer of one of the people is not complete unless he does wudoo’ … Then he says: Allahu akbar, then bows.” Classed as saheeh by al-Albaani in Saheeh Abi Dawood.
4. Because the points at which these adhkaar are recited are pillars or essential parts of the prayer, dhikr at these points is obligatory, just as there are words to be recited when standing.
With regard to the hadeeth about the one who prayed improperly, it is mentioned in the hadeeth that we narrated that he (the Prophet, blessings and peace of Allah be upon him) taught him that. It is something additional that must be accepted [[cxn??] The Prophet (blessings and peace of Allah be upon him) did not teach you all the obligatory parts of the prayer, based on the fact that he did not teaching the tashahhud or the salaam. So it is to be understood as meaning that he limited it to teaching him only that which he had seen him doing improperly. End quote.
It says in al-Mawsoo ‘ah al-Fiqhiyyah (4/40):
When sitting between the two prostrations, it is Sunnah to pray for forgiveness, according to the Hanafis, Maalikis and Shaafa ‘is, and it is one opinion that was narrated from Ahmad. The basis that is to be found in the report narrated by Hudhayfah, according to which he prayed with the Prophet (blessings and peace of Allah be upon him) and he used to say between the two prostrations: “Rabb ighfir li, Rabb ighfir li (Lord forgive me, Lord forgive me).”
However, asking for forgiveness here is not obligatory, because the Prophet (blessings and peace of Allah be upon him) did not teach it to the one who prayed improperly. The well-known view of the Hanbalis is that it is obligatory. This is also the opinion of Ishaaq and Dawood, and aqallahu one time [??]. End quote.
This is a matter concerning which there is a difference of opinion among the scholars. The most that can be said is that the view of the Hanbalis, that the takbeers of movement are obligatory, is more likely to be correct, because of the evidence mentioned above, and because the Prophet (blessings and peace of Allah be upon him) said: “The imam has been appointed to be followed, so when he says takbeer, then say takbeer…” Narrated by Muslim, no. 411.
With regard to the du ‘aa’ between the two prostrations, the opinion of the majority, which is that it is mustahabb, is more likely to be correct, because there is no evidence to clearly indicate that it is obligatory.
it is better for the worshipper to recite du ‘aa’s that have been narrated in the texts between the two prostrations. With regard to adding to the du ‘aa’s that have been narrated, or saying a du ‘aa’ that was not narrated, what appears to be the case is that it is permissible. This has been discussed previously in the answer to question no. 176496.
And Allah knows best.