Why Should Prayer Be in Arabic?
Salah must be performed in the same manner as Prophet Muhammad (peace and blessings be upon him) performed it; he said:
Pray as you have seen me praying.
A person capable of speaking or learning Arabic is not allowed to pray in a non-Arabic language. The essential utterances and recitations made during Salah, especially those from the Noble Quran, must be said in Arabic.
The Quran is the direct, literal Word of Allah, revealed to humankind in Arabic; not a single word or letter of it may be changed or substituted. Any translation of the Glorious Quran, into any language, is not Quran, but merely a translation of an interpretation of some of its meanings. It does not have the sanctity of the Quran and one cannot use it for recitation in Salah.
In the Case of Recent Muslims Who Have Not Yet Learned Arabic and Those Who Cannot Learn It
1. Learn the Opening Chapter at Least
If you are a recent Muslim, make your best effort to learn Al-Fatihah.
It is an integral pillar of Salah, without which it is invalid. Prophet Muhammad (peace and blessings be upon him) said:
There is no Salah for the one who does not recite the Opening of the Book (Al-Fatihah). (Narrated by Al-Bukhari)
2. Memorize the Essential Phrases
Try your hardest to also memorize the essential phrases that must be said during Salah.
They are only valid in Arabic. These phrases are: Allahu Akbar (Allah is Greater), Subhana Rabbiyal Azim (Glory be to my Lord, the Most Great), Sami`a Allahu liman hamidah (Allah listens to those who praise Him), Rabbana wa lakal-hamd (our Lord, and to You is due all praise), Subhana Rabbiyal A`la (Glory be to my Lord, the Most High), and the formulas of Al-Tashahhud, Al-Salat-ul-Ibrahimiyyah, and Taslim.
3. Learn Dhikr
If the time of one of the five daily prayers becomes due before you have learned how to recite Al-Fatihah in Arabic, you may instead say: Subhan Allah (Glory be to Allah), Alhamdu lillah (all praise is due to Allah), La ilaha illa Allah (there is no god but Allah), Allahu Akbar (Allah is Greater), and La hawla wala quwwata illa billahil-`Aliyil-`Azim (there is neither might nor power except with Allah, the Most High, the Most Great).
This is based on the following hadith:
“A man came to the Prophet (peace and blessings be upon him) and said:
‘I cannot learn anything of the Quran, so teach me something that I can say instead of reciting the Quran.’
He (peace and blessings be upon him) replied:
Say: Subhan Allah, alhamdu lillah, la ilaha illa Allah, Allahu Akbar, wa la hawla wala quwwata illa billahil-Aliyil-`Azim. (Narrated by Abu Dawud)
4. Pray in Congregation
Be keen during this initial phase to pray in congregation.
This will help you improve and perfect your Salah. Also, the reward for praying in congregation may offset shortcomings or mistakes you may make while learning how to pray.
Only the original Arabic text of the Quran is divine. Any translation of its meaning is but a human endeavor.
Muslims Who Have Difficulty or Cannot Learn Arabic
Scholars have made a distinction between people capable and incapable of learning Arabic. As long as you are capable, do your best until you can recite Al-Fatihah and the essential utterances of Salah.
If you have difficulty learning Arabic, you should at least learn Al-Fatihah, and you can recite the essential utterances of prayer in your own language.
If you have only learned part of Al-Fatihah, you should recite Al-Fatihah as best as you are able, and then glorify Allah, praise Him, magnify Him, and proclaim His Oneness, so that these words of remembrance make up for whatever parts are left out of Al-Fatihah.
However, if after much effort you still cannot learn Al-Fatihah at all or anything of the Quran, you are exempted from the obligation of reciting the Quran on account of your inability to learn it. Allah Says:
Allah burdens not a soul beyond its capacity. (Quran 2:286)
You should instead recite the five utterances of remembrance prescribed by Prophet Muhammad (peace and blessings be upon him).