Rulings on Supplication during Sajdah
(a) While offering Sajdah in a regular prayer (salah) the medium of supplication should always be Arabic language. It is not permissible to use any other language during salah.
(b) One should restrict himself, as far as possible, to the supplications contained in the Holy Qur’an and Sunnah. However, if one likes to pray in his own Arabic words, the prayers should be restricted to those things only which cannot be asked from a human being, such as
“O Allah, forgive my sins and the sins of my wife and my children.”
This Arabic supplication is permissible because forgiveness of sins cannot be asked from a human being but those things which can be asked from a human being cannot be asked in a prayer offered while performing salah, such as (O Allah, make me marry such and such woman). If somebody prays for such mundane things which can be asked from a human being also, the salah will be rendered void, even if the medium of prayer is Arabic language.
(c) Although offering supplications during sajdah is permissible with the conditions mentioned above, it is more advisable to avoid it during the Fard salah, and restrict it to the Nawafil only.
All the rules mentioned above relate to the supplications offered in a sajdah which forms part of salah. However, if someone makes a sajdah out of salah for the purpose of supplications only, there is no prohibition, nor is it necessary to observe the conditions mentioned in (a), (b) or (c) above. In such a position one can pray in whatever language one deems fit.
It is, therefore, permissible to make sajdah for the purpose of supplication after the salah is over. However, this should not be made a permanent practice after every salah, because the Holy Prophet (S.A.W.) used to pray after salah in a sitting position, and it is in no way advisable to leave this sunnah of the Holy Prophet (S.A.W.) forever.