Prayer in One’s Mother Tongue
The previous hadith mentions the prayer of a Companion. The Prophet of Islam said that this prayer was a prayer with ism-e-aazam. Since this prayer was said by the Companion in the Arabic language, people consciously or unconsciously regard that a prayer with ism-e-aazam is one which is done in the Arabic language, and a prayer not said in the Arabic language is not the prayer of ism-e-aazam.
But this thinking is not right. In its reality, the prayers said by the Companions, were in their own mother tongue, rather than in the Arabic language. Associating prayer with the Arabic language, is an unnatural concept. Dua, or prayer, is another name for the feelings of the heart, rather than just any linguistic sequence. The Quran tells us that “each Prophet was sent in the language of his own community.” (14:4). The same is true of dua. Just as the calling of people to God is done in the language of one’s own community, dua is also said in the mother tongue of the individual.
If prayer were associated with the Arabic language alone, and if the prayer in Arabic language were regarded as superior prayer, this would amount to nullifying the actual spirit of prayer. Prayer is not just the repetition of certain words. Prayer means calling upon God or praying to God with one’s heart and mind, and such prayer will always come to one’s lips only in one’s mother tongue
Source: Attributes Of God