Assalamualaykoum warahmatullah wa barakatu,
Please forgive me if I am incorrect but I believe it is wrong to utter prayers in Arabic only. The reason I believe this is because to me it is limiting. This is like saying Allah (swt) only understands Arabic, astaghfirullah. I believe prayer can be made in any language for the language of intention is the truest language of prayer.
Prayer as in Salah, is not performed as anyone likes or wishes, or how one believes it should be. Otherwise there is no point in having a Prophet to teach us and to be followed. Prophet Muhammad s.a.w. taught us how to pray properly and says which means, “Pray as you have seen me praying” (Bukhari). This means the prayer (Salah) that Muslims perform must follow in the manner done by him (s.a.w.), and so include the aspects of Intention, Movement and Recitation – which is in Arabic.
With regards reciting a prayer (Du’a/supplication or Dhikr) in Sajdah whether as part of Salah or outside of it (e.g. Sujud Shukr, Sujud Tilawah etc) the recitation must be in Arabic. Here are two instances:
– If the one who is praying knows Arabic, his prayer will be invalidated by a non-Arabic supplication (du‘a) or invocation (dhikr), whether or not this supplication or invocation has been transmitted from the Prophet s.a.w. [at that point in prayer] or not.
– As for the one who does not know Arabic, it is permitted for him to make a supplication or invocation in a language other than Arabic, but only if it has been transmitted that the Prophet s.a.w. uttered them [at that point in the prayer]; otherwise, if they haven’t been transmitted from the Prophet s.a.w., saying them in a language other than Arabic will invalidate the prayer.
If you refer to prayer as in making Du’a outside of Salah, then there is no problem to do it in any language.