In The Name of Allah, The Most Merciful, The Bestower of Mercy.

Al-Allamah Abdullah Al-Bukhari, may Allah preserve him, said:

From that which the people of knowledge have affirmed is that this religion is established on two matters: Clarification of the truth and refuting (or rejecting) falsehood and its people. The affirmation of this becomes manifest to the one who contemplates the statement of Tawhid [لا إله إلا الله] with clarification and explanation. The saying of a servant (of Allah) لا إله is a refutation against falsehood and its people- those who deify others besides Allah. The statement إلا الله is an affirmation of truth and a clarification of it. It (means) that Allah alone has the right to be worshipped and He has no partner.

Likewise, the statement محمد رسول الله is an affirmation of the Messenger ship of the Prophet, peace and blessings of Allah be upon him, and a refutation against the one who gives him a status above that and thus deifies him, or lowers the rank of his Prophethood and Messenger ship.

An Excerpt from Al-Maqaalaat Ash-Shar’iyyah pages 14-15