Answer
Shahada is Arabic for “testimony” or “witness.” The Shahada is the first pillar of Islam and is the Islamic creed:
“There is no god but Allah, and Mohammad is the messenger [or prophet] of Allah.”
Transliterated from the Arabic, the Shahada looks like this: La ilaha illa Allah wa-Muhammad rasul Allah.
The Shahada is a declaration that all Muslims must make, and anyone who cannot make this declaration cannot be considered a true Muslim. This confession uttered before two Muslim witnesses is all that is required to become a Muslim. The Shahada is repeated at each of the five daily prayer times that Islam requires.
The first part of the Shahada confession affirms that Allah is one—thus, polytheism and the Christian doctrine of the Trinity are denied.
The second part of the confession affirms that the primary communication from Allah to mankind is through Mohammad—thus, Jesus and the Bible are relegated to a lower status.
In Shia Islamic practice, the Shahada has a third phrase: “Ali is the wali of Allah.” Wali literally could be translated “guardian” or “protector” but is commonly used to refer to a Muslim saint or “friend of Allah.” Shia Muslims consider Ali (son-in-law of Mohammad) as the legitimate successor to Mohammad—a point that Sunni Muslims reject.
The Shahada is normally found on flags of Muslim countries as well as on the flags of the Taliban, ISIS, and Hamas.