Sincerity (ikhlaas) is a necessary condition in all acts of worship, and no act of worship is valid if anything or anyone is associated with Allaah. Allaah says (interpretation of the meaning):
So whoever hopes for the Meeting with his Lord, let him work righteousness and associate none as a partner in the worship of his Lord
And they were commanded not, but that they should worship Allaah, and worship none but Him Alone (abstaining from ascribing partners to Him), and perform As‑Salaah (Iqaamat‑as‑Salaah) and give Zakaah, and that is the right religion
[al-Bayyinah 98: 5]
So worship Allaah (Alone) by doing religious deeds sincerely for Allaah's sake only.
3. Surely, the religion (i.e. the worship and the obedience) is for Allaah only
According to a saheeh hadeeth qudsi, the Prophet (peace and blessings of Allaah be upon him) said: Allaah, may He be blessed and exalted, says: I am so self-sufficient that I am in no need of having an associate. Thus he who does an action for someone else's sake as well as Mine will have that action renounced by Me to him whom he associated with Me.'
What is meant by sincerity towards Allaah in worship is that nothing motivates the person to do that act of worship except love and veneration for Allaah, and the hope for His reward and pleasure. Hence Allaah says of Muhammad the Messenger of Allaah (peace and blessings of Allaah be upon him):
Muhammad is the Messenger of Allaah. And those who are with him are severe against disbelievers, and merciful among themselves. You see them bowing and falling down prostrate (in prayer), seeking Bounty from Allaah and (His) Good Pleasure
[al-Fath 48:29 - interpretation of the meaning]
No act of worship, whether it is Hajj or anything else, will be accepted if a person is doing it to show off to other people, or he is doing it so that other people will see him and say, How pious So and so is, how much he worships Allaah and so on.
No worship will be accepted if the motivation behind it is to see places or see people, or other such things that are contrary to sincerity. Hence the pilgrims who go to the Sacred House must make their intention sincerely for the sake of Allaah and not make it their intention to see the Muslim world, or to do business, or so that it will be said that So and so goes for Hajj every year, and so on.
There is nothing wrong with a person seeking the bounty of Allaah by doing business whilst travelling to the Sacred House, because Allaah says (interpretation of the meaning):
There is no sin on you if you seek the Bounty of your Lord (during pilgrimage by trading)
What goes against sincerity is when a person's only intention is to business and earn money. This is a person who seeks worldly gain by doing actions that have to do with the Hereafter. This means that the act of worship is invalid or that it is sorely lacking. Allaah says (interpretation of the meaning):
Whosoever desires (by his deeds) the reward of the Hereafter, We give him increase in his reward, and whosoever desires the reward of this world (by his deeds), We give him thereof (what is decreed for him), and he has no portion in the Hereafter
Reproduced from Islam QA