Tawheed is the key

Sincerity

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.]

This hadeeth is one of the hadeeth around which the whole religion revolves, and it is related from Imaam ash-Shaafi’ee that he said, “This hadeeth constitutes a third of all knowledge.”

Imaam Ahmad said, “The foundations of Islaam are upon three ahaadeeth:· The hadeeth of Umar, ‘Verily actions are by intention’
· The hadeeth of Aa`ishah, ‘Whoseover introduces into this affair of ours that which is not part it, then it is rejected.’
· The hadeeth of Nu`maan bin Bashir, ‘The halaal is clear and the haraam is clear.’”

Ishaaq bin Raahawayah said, “the foundations of the religion are upon four hadeeth:· The hadeeth of Umar, ‘Verily actions are by intention.’
· The hadeeth, ‘The halaal is clear, and the haraam is clear.’
· The hadeeth, ‘Verily the creation of one of you comes together in the stomach of his mother for 40 days.’
· The hadeeth, ‘Whosoever invents into this affair of ours anything which is not part of it, then it is rejected.’”

Abu Ubayd said, “The Prophet, sallallaahu ‘alayhi wa sallam, collected all the affairs of the Hereafter in one statement, ‘Whosoever introduces into this affair of ours that which is not part of it, then it is rejected.’ And all the affairs of this world in one statement, ‘Verily actions are by intentions.‘ Place them in every chapter.”

Abu Daawood said, “I looked into the hadeeth of the Musnad (i.e. of Ahmad) and it consisted of 40 000 ahaadeeth. The I looked again and (found that) the 40 000 ahaadeeth revolved around 4 ahaadeeth:

· The hadeeth of Nu’maan bin Bashir, ‘The halaal is clear and the haraam is clear.’ · The hadeeth of Umar, ‘Verily actions are by intentions’
· The hadeeth of Abu Hurayrah, ‘Verily Allaah is pure, and does not accept except that which is pure. And indeed Allaah ordered the Muslims with that which He ordered the Messengers.’
· The hadeeth, ‘From the excellence of ones Islam is his leaving that which does not concern him.’”

From: The Hadeeth of Intention
Imaam Ibn Rajab al-Hanbali rahimahullah
Jaami ul-Uloom wal-Hikam