Intention

Umar bin al-Khattaab relates that: 'I heard the Messenger of Allaah, sallallaahu 'alayhi wa sallam, saying, "Verily actions are by intentions, and for every person is what he intended. So the one whose hijra was to Allaah and His Messenger, then his hijrah was to Allaah and His Messenger. And the one whose hijrah was for the world to gain from it, or a woman to marry her, then his hijrah was to what he made hijrah for." [Related by Bukhaaree and Muslim.]

Intention is very important in Islam because all deeds are based upon it. Actions
are not accepted without an intention.

Niyyah (intention) in the language is a type of desire (iraaadah) or a driving force
in the heart towards a deed. You should have the intention at the exact same time
you want to do an action. Your heart will be tied with the intention and you cannot remove it. Intention is not a statement of tongue: “O Allah, I intend such and such…” nor is it a thought in the mind. It is a driving force or a desire to do something. Your intention is already there, you should not say anything inside.

The reason behind intention is to differentiate between actions such as zuhr salat
and asr salat. Intentions have to be directed only for the sake of Allah. This is called Ikhlaas (purity). The Quran talks about the importance of having correct and sincere intentions. Allah Subhana wa Ta’ala says:
“Yet they were commanded nothing but to worship Allah, with their sincere
devotion to Him.” {Surah al-Bayyinah 98:5}

and also, Allah said:

“He that desires the transitory things of this life, We readily grant him such things as We please to whomsoever We want, then We condemn him to hell, where he will burn, disgraced and rejected. He that desires the life of the hereafter and strives for it as best as he can provided he is a Believer, the endeavor of every such person will be accepted.” {surah Al-Israa 17:18-19}
And also:

“O Prophet, you are not responsible for their guidance, it is Allah Who guides whom He pleases. Whatever wealth you spend in charity, it is to your own advantage; provided you give to seek the pleasure of Allah.” {Surah al-Baqarah 2:272}

We have already mentioned the hadeeth from Umar Ibn Al-Khattab “Verily actions are by intentions (innammal a’maalu bin niyyat)”. This shows that actions are done by intentions. Abu Ammaar Yasir Al-Qathi said:

“The hadeeth on intention indicates that every delibrate action of a person has an
intention behind it. The intention may be praiseworthy, condemnable, or neither of the two, but an intention must exist. In other words, every action that a person performs has a goal or a purpose. The Prophet (sallallahu alayhe wa sallam) went on to say that every person will achieve that which he intended.”
 {Riyaa – Hidden Shirk, page 18}

Allah’s Messenger (sallallahu alayhe wa sallam) also said:
“Certainly, Allah does not look at your appearance or wealth. But He only looks at
your hearts and deeds.” (Bukhari and Muslim)

Abu Bakr Al-Jaza’iry said: “Looking at the hearts means looking at the intentions, for it is the intention that is the driving and motivating force behind the deed.
Allahs Messenger (sallallahu alayhe wa sallam) also said: ‘He who seriously considered doing a good deed but did not do it, will have one good deed recorded for him.’ (Muslim).
  Just Seriously considering a good deed is a good deed itself by which one earns a
reward. This is due to the virtuousness of having a proper intention.” {Minhaj Al-
Muslim, Volume 1, page 145-146}

The Messenger (sallallahu alayhe wa sallam) also said, "People will be gathered
upon their intentions" [Ibn Maajah, Saheeh al-Jaami no.7898]

The early generation of the Muslims realized the great importance of sincere and
correct intentions. We conclude by presenting to you statements of the early generations about correct and sincere intention from the book Jaami’ al-Uloom
by Imam Ibn Rajab Al-Hanbali:

Fudayl bin `Iyaadh said about His saying, 'That he may test which of you is best in action' (67:2) - "Who is sincere in it and correct in it. And the action, if it is sincere and not correct then it is not accepted. And if it is correct and not sincere then it is not accepted. It is only accepted when it is both sincere and correct. And it is sincere when it is for the sake of Allaah, and correct when it is done according to the Sunnah."

Yahya bin Abu Katheer said, "Learn your intention for it is more serious than the
action."

Zayd ash-Shaamee said, "verily I like that I have an intention for everything even if it be eating and drinking"
And he also said, "have intention for everything, desiring the good, even if it be leaving for the toilet"

Ibn al-Mubaarak said, "maybe a small action is made great by its intention, and maybe a great action is made small by its intention"

Ibn `Ijlaan said, "the action is not acceptable except by three: Taqwaa of Allaah, and good intention, and correctness (i.e. conformity to the Sunnah)"

Fudayl bin Iyaadh said, "Allaah wishes from you only your intentions and desires
(iraadah)"

Wal hamdulillahi Rabill alamin.

Source: Abul Ghaazi Al-Iraqee