The Qur’an teaches us that when Adam sinned, he could not utilize his own words to repent and express his remorse; God taught him the exact words whereby he repented and was redeemed (see Qur’an 2:37).
Similarly, God has given us specific words - the words of Al-Faatehah - in order to establish daily contact with Him (Salat), and redeem ourselves. As proven by the awesome mathematical miracles presented in Religious Duties: A Gift From God and January 1990 Submitters Perspective, every single letter in Sura 1, Al-Faatehah, is divinely designed.
The word “SALAT” is rooted in the Arabic word “SILAT” which means “CONNECTION.” As pointed out in the August 1985 and February 1986 Submitters Perspectives, this CONNECTION cannot take place unless the numerical structure of the liturgy is strictly observed.
Unfortunately, Satan has succeeded in altering the Salat prayers for millions of Muslims, thus depriving them of making contact with their Creator. First, he talked them into adding the word “AMEEN” at the end of Al-Fatihah. This word is foreign, not Arabic, and is never mentioned in Qur’an. But it effectively destroys the numerical structure of the Salat words by adding more letters and sounds.
Ironically, Satan convinced people to drop the the first and most important verse of thc Quran; In the Name of God, Most Gracious, Most Merciful, from the beginning of Al-Fatehah. And add this foreign word "Ameen" at the end. According to the corrupted jurisprudence --listen to this -- "Bismillah is 'Makrooh.’" The word "Makrooh" means "Hated!" Can you believe it? Here is the reference from the classic book: "Jurisprudence According to the Four Sects," (Dar AI-Fikr, Beirut), '69, Pg 257.
By cancelling the 19 letters of Bismillah and adding 'AAAMEEEN," Satan ensures that those people establish contact with him, not with God.
The gematrical value of Basmalah is 786, and the value of 'Ameen" is 102. By removing Basmalah and adding 'Ameen," the Mohamedans' net result is 102–786 = – 684, and 684 is the gematrical value of 'Al-Quran Al-Kareem." This informs us that since the Mohamedans lost "The Key," they have no access to the Quran. This explains the famous strange phenomenon that the Arabs keep saying that the Quran is "difficult to understand," even though God repeats in the Quran that He made the Quran easy.
To summarize, we must not say "Ameen" (or any similar utterance) after Al-Fatehah in our Salat.
Reference:
Great Tragedy in Mecca, Submitters Perspective, January 1990