Now let me tell you the purport of the Kalima as also what actually does a man affirm by reciting it and what obligations devolve on him after this affirmation ?
The meaning of Kalima is that there is no god save Allah and Muhammad (peace be upon him) is the Messenger of Allah. The word " Allah " found in the Kalima means God. Now, that being is called God Who is Master, Creator, Nourisher, and Sustainer, Who listens to our prayers and grants them, and Who is worthy of our worship. Now that you have said : La ilaha illallah, it would mean that, firstly, you have acknowledged that this world has not come into being without the creative power of God, nor is it a fact that it has many gods. Actually, it does have a God and that God is just one, and there is no other being except Him Who wields Divine power. Secondly the other point which you affirmed on reciting the Kalima is that this very God Who is your God, is also God of the whole world. Each and every thing owned by you and by the world belongs to Him. It is He Who is the Creator and the Nourisher. Life and death are under His command. Trouble and comfort are also from Him. Whatever one gets, is really given by Him. Whatever is taken away from anybody, is in reality due to His command. He alone should be feared. He alone should be entreated to fulfil our needs. Before Him alone we should bow our heads. He alone deserves to be worshipped. We are not slaves or servants of anybody save Him, nor is anyone our Master or Sovereign. Our real duty is to exclusively comply with His orders and obey His laws.