Taken from Explanation of Important Lessons for Every Muslim
Compiled by Abu Aadil Shahadathain - The Testimony
The testimony (LA ILAAHA ILLA ALLAH ) comprises two concepts: Denial and Affirmation.
I: The testimony of faith denies the attribute of divinity to anyone and anything other than Allah - the Exalted. All those other than Allah, such as the angels, the Prophets, and the rest of Mankind, let alone the idols and the political regimes in the world, are not gods and thus don’t deserve to be worshipped. Therefore, denial in this respect is not denial of the existence of the alleged gods, rather the denial of divinity which is attributed to them.
II.The testimony of faith affirms and restricts divinity to Allah alone. That is, the slave must believe that Allah is the only true God, and accordingly dedicate no act of worship to any, other than Allah.
A confession with your tongue but a heartfelt belief, “O Allah! I testify that Muhammad (Peace be upon him) is Your Messenger.” That means that none has the right to be followed after Allah, but the Prophet Muhammad (Peace be upon him) as he is the Last of His Messengers. As Allah said:
“Muhammad (Peace be upon him) is not the father on any man amongst you but he is the Messenger of Allah and the last (end) of the Prophets and Allah is Ever All Aware of everything.” (V.33:40)
“And whatsoever the Messenger Muhammad (Peace be upon him) gives you, take it and whatsoever he forbids you, abstain from it.” (V.59:7)
And Allah said: “Say (O Muhammad) (to mankind) ‘if you (really) love Allah, then follow me’.” (V.3:31)
As for the others than Muhammad (Peace be upon him) their statements are to be taken or rejected as to whether these are in accordance with Allah’s Book (i.e. the Quran) or with the Sunnah (legal ways, orders, acts of worship, statements etc.,) of the Prophet (Peace be upon him), or not.