Know that this great word entails, a fortiori, that Muhammad (asws) is the Messenger of Allah. This is because the meaning of La ilaha illa Allah is that there is nothing worthy of worship in truth—nothing that should be worshipped—other than Allah. He Alone is the One who should be worshipped and it is obligatory for the servants to worship Him. That is a right He has over them, considering that He is their Lord and they are His slaves.

La ilaha illa Allah entails that Muhammad (asws) is the Messenger of Allah
Imam `Abdallah Sirajuddin al-Husayni