I already have studied the Torah (Old Testament) and I'm now studying the New Testament and The Holy Quran.
I have a question regarding prophets.
How come Muslims believe in prophets after Malachi since in the Torah it's said that in Yehoshua 23:6:
וַחֲזַקְתֶּם מְאֹד--לִשְׁמֹר וְלַעֲשׂוֹת, אֵת כָּל-הַכָּתוּב בְּסֵפֶר תּוֹרַת מֹשֶׁה: לְבִלְתִּי סוּר-מִמֶּנּוּ, יָמִין וּשְׂמֹאול
Be very strong to protect and do everything that is written in Moshe's Torah. Do not deviate from it to the right or to the left.
In Deuteronomy 4:2 :
... לֹא תֹסִפוּ, עַל-הַדָּבָר אֲשֶׁר אָנֹכִי מְצַוֶּה אֶתְכֶם, וְלֹא תִגְרְעוּ, מִמֶּנּוּ
Do not add onto what I am commanding to you, and do not detract from it...
Proverbs 30:6 :
אַל-תּוֹסְףְּ עַל-דְּבָרָיו: פֶּן-יוֹכִיחַ בְּךָ וְנִכְזָבְתָּ
Do not add onto [God's] words, lest he test you and you be found to be a liar.
Rambam writes in his Mishneh Torah about it :
לפיכך אם יעמוד איש בין מן האומות בין מישראל ויעשה אות ומופת ויאמר שה' שלחו להוסיף מצוה או לגרוע מצוה או לפרש במצוה מן המצות פירוש שלא שמענו ממשה או שאמר שאותן המצות שנצטוו בהן ישראל אינן לעולם ולדורי דורות אלא מצות לפי זמן היו הרי זה נביא שקר שהרי בא להכחיש נבואתו של משה ומיתתו בחנק על שהזיד לדבר בשם ה' אשר לא צוהו
Therefore, if a person will arise, whether Jew or gentile, and perform a sign or wonder and say that God sent him to:
a) add a mitzvah,
b) withdraw a mitzvah
c) explain a mitzvah in a manner which differs from the tradition received from Moses, or
d) if he says that the mitzvot commanded to the Jews are not forever, but rather were given for a limited time,
he is a false prophet. He comes to deny the prophecy of Moses and should be executed by strangulation, because he dared to make statements in God's name which God never made.
All these sources, from original holy scripture but also from commentaries express that nothing may be added or subtracted from the Torah. Even someone who claims to be a prophet may never do so, and to attempt to do so will show him to be a false prophet. So how come Muslims believe in the Torah/Old Testament but also believe in prophets such as Jesus (pbuh) and Muhammad (pbuh)?
Thank you for your help and guidance.