Allah is saying, I know how much you're capable of and if I were to give you everything then you would go beyond what is Halal, what is permissible for you and this same sentiment is demonstrated in the Seerah of the Prophet (sallallahu alayhi wa salam) in a Hadith in Sahih Bukhari, it is narrated that the Prophet Muhammad (saw) was giving a group of people money, one of the companions said: o Messenger of Allah, why don't you give so and so? for by Allah I think he is a Mumin, he is a good guy, give it to him and the Prophet Muhammad (saw) ignore him and He kept on giving to other people, second times the Sahaba said: o Messenger of Allah give to him for Wallahi I think he is a Mumin and He ignored him for a second time, a third time He ignored him and then our Prophet Muhammad (saw) turned and said to him: sometimes I give money to people and I don't give to those whom I love more I.E, the beloved I don't give to, out of a fear that the money will be a temptation that will drag them in to Hellfire, in other words our Prophet knows the people!
Prophet Muhammad (saw) is saying, what you're saying about this man might be right, he is a mumin, he is a good guy but he doesn't have that type of, if you like, patience with money and he might do something that is not appropriate with that money. My dear brothers and sisters what do we learn from this Ayah and from this Hadith is very simple and that is, what we do not have and we try to get it, we didn't get it, we should be content that Allah has a plan, that Allah knows how much He is giving.
Allah reveals with his Qadr as much as He pleases (to) that person. In the end of the same Surah, Allah mentions the same fact but this time about children, Allah says in the Quran: He is the one who blesses with children, ''to some he gives all daughters''-''to some he gives all men, all boys''-'' and some families they have ''boys and girls'' and some people have no children.
This is the Qadr of Allah (subhana WA Ta'ala). Allah knows who to give what to and Allah knows how much to give and Allah knows who to test people with and therefore the believer who believes in Qadr, one of the main benefits of believing in Qadr is that you feel a contentment of the heart. Whatever has happened has happened because of Qadr and as I said many times Qadr is used to calm down and to find release from a calamity and Qadr is not used to justify a sin.
Qadr is used to find peace in whatever Allah has decreed. You didn't get the job QaddarAllah. You didn't make the million that you're looking to get from the business QaddarAllah. You didn't have this, you didn't get that, you tried, you made dua to Allah, you didn't get it, now the point is you have to try, if you didn't try then that's your problem but you have to try, you want the job, you want the business, you want to get married, you try, if it doesn't happen that's when we say QaddarAllah.