A few years back, one of my Muslim friend told me that it will be good to do Du'a during the second last Raka'h (during prostration) after saying "Subhana Rabbiyal Alaa Wabahamdi-3" of each obligatory Waajib prayer, and I have been doing that since.. But my husband who follows a different scholar told me that I am not allowed to do any kind of Du'a while performing my Waajib prayer, instead I should do Du'a after the Waajib prayer has been performed. Kindly explain to me if this is true and also what will happen to all my prayers performed in the past few years.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Saying that supplicating while in prostration and when performing an obligatory prayer is not permissible is wrong, and this is speaking on behalf of Allaah without any knowledge. So your husband should fear Allaah and stop giving Fataawa. Rather, supplicating while in prostration is desirable whether that is during an obligatory or a supererogatory prayer. Indeed there are many Prophetic narrations proving that this is desirable.

The Prophet said: "The servant is nearest to his Lord when he is in prostration. So, supplicate as much as possible while in this state." [Muslim] The Prophet further said: "Strive your hardest in supplicating when in prostration. Most likely, your supplications will be granted." [Muslim]

In fact the Prophet used to say the following supplication when in prostration: "O Allaah, forgive me all of my sins, the small and great of them, the first and last of them, and the seen and hidden of them." [Muslim]

There are other evidences in this regard. So a Muslim can say any supplication in order to achieve the benefits of this world and those of the Hereafter. Indeed many scholars stated that it is desirable to supplicate while in prostration.

There are other cases where supplication is desirable, like after finishing the last Tashahhud and before concluding the prayer [by saying 'Salaam']. It is confirmed that the Prophet said: "If you finish your last Tashahhud [and before saying Salaam] you have to seek refuge in Allaah from four things: Say: (Allaahumma innee a'oothu bika min 'athaabil-qabr, wamin 'athaabi jahannam, wamin fitnatil-mahya walmamaat, wamin shari fitnatil-maseehid-dajjaal.) "O Allaah, I take refuge in You from the punishment of the grave, from the torment of the Fire, from the trials and tribulations of life and death, and from the evil affliction of Al-Maseeh Ad-Dajjal (Antichrist)."

Therefore, you should know that you are correct in supplicating the way you mentioned, and you acted according to the Sunnah. Your prayer is valid and you do not have to make it up. We ask Allaah to accept it from you. Finally, it should be noted that supplicating during the prayer is not specific to the last Rak'ah, for more benefit, please refer to Fatwa: 89716.

Allaah Knows best.