Schahada has 2 parts:

1) There is no god but Allah

2) Mohammed is His Messenger

Let me elaborate on the first part:

It means to deny any false deity (make kufr in it), accept Allah Ta'ala as the only God, accept His beautiful names and attributes, worship Him alone, believe that He is the sole Creator, Provider, Sustainer...

Rule only by His laws, believe that only His system is right and that islam is the only true religion.

The second part means to believe that Mohammed is the last Messenger, that he delivered words of Allah, and that his traditions are part of the Revelation.

The Shahadatan is blasphemous toward the God of the Bible because it attempts to place Muhammad in the position that only Jesus the Messiah can fill and even give Muhammad attributes that belong to deity, as Al-Insan Al-Kamel, the perfect man; Rahmatan-lil-A’alameen, a mercy to all mankind; Al-rasul Al-A’tham, greatest of all sent by God; Shafi, Healer; Munji, saviour; Mahdi guided one/deliverer; Mustafa, chosen;Amir, the prince; Awal, first; Akher, last; Rasul Al-Malahim, messenger of the Last-Days battles, and finally Muhammad, the praised one.

When the Muslim Mahdi sits in the Temple of God and while he declares that he is God (2 Thessalonians), he also worships “honours a god” (Daniel 11) and “advances its [this god’s] glory” (Daniel 11:39) and will not “honour the god of his fathers”, there's an ancient Bible that tells the name of the god of the Antichrist, Douay-Rheims Bible But he shall worship the god MAOZIM in his place: and a god whom his fathers knew not, he shall worship with gold, and silver, and precious stones, and things of great price (Verse 38).

(The Douay-Rheims Bible (1609) is the oldest full Roman Catholic Bible translation in English, making it older than the KJV).

Maozim is both a literal name and as in all semitic names, also has meaning (which the other translations state) also applies: “defense,” “fortress,” “fortresses,” “helmet,” “protection,” “refuge,” “safety,” “strength,” “strong,” “stronghold,” and “strongholds” “Allah Al-Mu’izz” can examine, not just that this is one of the names of Allah, but is also the same meaning which exactly matches the hebrew Maozim.

Indeed, he is Maozim (Al-Mu’izz), for the Antichrist “honors a God of fortresses,” who is a God of war and the sword while his name, literally in Hebrew, Moazim, a semitic name, is also in the Arabic Al-Mu’izz (Allah Al-Mu’izz الله المعز) is one of the ninety nine official names of Allah in Islam and Maozim also has the exact meaning in the Arabic: “to be mighty, potent, strong, powerful …”

While many spiritualize the mark, they need to look at the language. When we come to the biblical Greek word “charagma,” used for “mark” means “a stamp, an imprinted mark.”So a follower of Antichrist will have a stamp on some sort of material as a badge to be placed on the forehead or arm. In John’s time, the use for “charagma” was reserved for slaves in what was called a badge of servitude.”

So it’s a literal badge that declares slavery and ownership by the master and followers use it to demonstrate allegiance to this master. This would fit with Islam since according to Islamic theology, Muslims are “slaves of Allah.” Islam, after all, is the religion of submission.

These followers have an option to either place this badge of servitude on the foreheads or the arms. Western analysts think that the mark is placed on the hand. This is not necessarily the only spot. We know from the Greek word “DEXIOS,” which could also be translated “right side”, “right arm” or “right shoulder”.

To become a Muslim (literally means submitter), one must confess the Shahadatan declaration to demonstrate allegiance and servitude to Allah and Muhammad. This submission is always combined with commitment to fight the world, and this dear reader you know what it means ..

This declaration is worn by millions of Muslim Jihadists and it is fairly unique to Muslims and is becoming a prominent feature of the Jihadi movement.