Iman (Faith) is a statement of the tongue, an action of the limbs and a belief of the heart. It increases with obedience and decreases with disobedience.
"And they were commanded not, except that they should worship Allah alone, making the Religion sincere to Him, and establish the prayer, and give the Zakaah. And that is the right religion." [Surah Al-Bayyinah (98): 5]
So He has placed the worship of Allah, the sincerity of the heart, the establishment of prayer and the giving of Zakaah, all as being from the Religion (i.e. Iman).
The Prophet (pbuh) said: "Iman consists of more than seventy branches. The highest of them is to testify that La ilaaha illa Allah (None has the right to be worshipped except Allah). And the lowest of them is removing a harmful object from the road."
So he (pbuh) placed speech and action as part of Iman (Faith). Allah says:
"As for those who believe, it has increased their Iman." [Surah At-Tawbah (9): 124]
And He says:
"In order that they may grow more in Iman (Faith), along with their (present) Iman." [Surah Al-Fath (48): 4]
The Messenger of Allah (pbuh) said: "Whoever says: 'Laa Illaaha Illaa Allah' and he has in his heart Iman, the weight of a wheat grain, or a mustard's seed or an atom, he will be extracted from the Hellfire."
Therefore he (pbuh) has placed Iman at different levels.
The Speech Of Allah
The Quran Is The Speech Of Allah
The Believers Will See Their Lord On The Day Of Judgement
The Divine Decree And Ordainment Of Allah
Iman Is Speech And Action
Faith In Everything That The Messenger Informed Of
Muhammad, The Seal Of The Prophets