The phrase "La ilaha illallah Muhammadur rasulullah" is a fundamental declaration in Islam, known as the Shahada (testimony of faith). It translates to:

"La ilaha illallah": "There is no god but Allah."
"Muhammadur rasulullah": "Muhammad is the messenger of Allah."
This statement is the core of Islamic belief, affirming the oneness of God (Tawhid) and recognizing the prophethood of Muhammad (peace be upon him). It signifies that Allah is the only true deity, and that Muhammad is the final messenger through whom divine guidance was revealed to humanity.

The Shahada is recited by Muslims as an expression of faith and is an essential part of the Islamic creed. It also serves as a reminder of both the spiritual and moral principles that Muslims are to follow, centering their lives around the worship of Allah and following the teachings of His Prophet.