What is the point of promising the reward of a house in Paradise for some righteous deeds?
Question

There is a hadith saying that whoever prays all his sunnah prayers allah will build him a house in paradise, but the quran says that the people of paradise will get whatever they wish. Doesnt this contradict the quran? Saying that i have to do such and such so that allah will do so and so when allah tells us that whatever we wish we will get?
Praise be to Allah.There are reports which state that the reward for some particular righteous deeds is the building of a house in Paradise for the one who does that deed.
For example, there is the hadith of Umm Habeebah, who said: I heard the Messenger of Allah (blessings and peace of Allah be upon him) say: “Whoever prays twelve rak‘ahs every day and night, a house will be built for him in Paradise because of them.” Narrated by Muslim (728).
The Muslim may think that this and similar hadiths contradict some verses of the Qur’an – such as the verses in which Allah, may He be exalted, says (interpretation of the meaning):
{Indeed, those who have said, “Our Lord is Allah” and then remained on a right course - the angels will descend upon them, [saying], “Do not fear and do not grieve but receive good tidings of Paradise, which you were promised
We [angels] were your allies in worldly life and [are so] in the Hereafter. And you will have therein whatever your souls desire, and you will have therein whatever you request [or wish]} [Fussilat 41:30-31] –
as he thinks that so long as the one who goes to Paradise will have all that he desires, he may wish for whatever he wants of houses, and thus there is no need to regularly pray twelve rak‘ahs every day and night.
The response to that is: Allah, may He be exalted, has decreed rewards of this type for some righteous deeds, so that must inevitably be based on the utmost wisdom, and our trust in His wisdom, grace and justice means that we have no need to question it.
Allah, may He be exalted, says (interpretation of the meaning):
{He is not questioned about what He does, but they will be questioned} [al-Anbiya’ 21:23].
Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
Allah, may He be glorified, is the Creator, Lord and Sovereign of all things, and He has great wisdom in what He creates, great blessing and mercy both general and specific. He is not to be questioned about what He does, but they will be questioned, not just because of His might and power, but because of His perfect knowledge, might, mercy and wisdom.”" (Majmo ‘ al-Fataawa  8/79).
Ibn al-Qayyim (may Allah have mercy on him) said:
Allah, may He be glorified, is Most Wise and does not do anything in vain for no purpose, or with no interest to be served or wisdom which is the ultimate goal of His actions. Rather His deeds are based on the ultimate wisdom, because of which He does the action and His actions are done through causes by means of which He does them. This is indicated by His words and the words of His Messenger, which are mentioned in so many religious texts that they are uncountable and cannot all be listed." (Shifa’ al-‘Aleel  p. 190).
Some of the reasons we may find for a promise such as this promise of a house in Paradise include the following:
1.. Specifying a particular reward for some righteous deeds is something that energizes a person and increases his desire to do the righteous deed, because this promise is something more than merely being admitted to Paradise, for it is enjoying that specific blessing. This is something that a Muslim feels in his heart.
2.. It may be that these houses will have some extra virtue or quality that makes them surpass  any other houses that the believer may wish for in Paradise, as the scholars said regarding the hadith of ‘Uthmaan ibn ‘Affaan, who said: I heard the Messenger of Allah (blessings and peace of Allah be upon him) say: “Whoever builds a mosque – Bukayr said: I think he said: seeking thereby the Countenance of Allah – Allah will build something like it for him in Paradise.” Narrated by al-Bukhaari (450) and Muslim (533).
Ibn Rajab (may Allah have mercy on him) said:
With regard to the words “something like it,” that does not mean something of similar size or similar quality in its construction. Rather what is meant – and Allah knows best – is that He will make his house commensurate with the size of the mosque built, and will make it well-built commensurate with how well-built the mosque was, not in terms of decoration. And the Muslim will benefit greatly from what is built for him in Paradise, commensurate with how much the people benefitted from the mosque he built for them in this world, and this house will surpass all other buildings in Paradise as the mosques were superior to all other buildings in this world." (Fath al-Baari  3/320-321).
These houses can only be attained by doing the righteous deeds that are stipulated in order to attain them; they are not like the blessings that may be granted in Paradise as soon as the believer wishes for them.
3..  Even if the believer can have whatever he wishes for in Paradise, we do not know whether he will wish for this particular blessing or not.
For it may never occur to him to wish for this blessing, so he will not attain it.
It is known that the people of Paradise will vary in their blessings, so it will not be possible for anyone to ask for a higher level, otherwise that would mean that the people of Paradise would all be on the same level with regard to blessings.
And Allah knows best.