the reality of the life of this world

Allah has clarified to us the reality of the life of this world and has informed us that it is like a fleeting shadow. (Know that the life of this world is but amusement and diversion and adornment and boasting to one another and competition in increase of wealth and children - like the example of a rain whose [resulting ] plant growth pleases the tillers; then it dries and you see it turned yellow; then it becomes [scattered ] debris. And in the Hereafter is severe punishment and forgiveness from Allah and approval. And what is the worldly life except the enjoyment of delusion.) [ 57:20 ]

He explained that it is a trial and that its delights would busy one and cause them to forget Allah. Therefore, one must be careful. Allah says: (So whatever thing you have been given - it is but [for ] enjoyment of the worldly life. But what is with Allah is better and more lasting for those who have believed and upon their Lord rely.) [ 42:36 ]

He explained that the life of this world is not permanent; rather it would lead one to eternal life. The life of this world is like a plot of fertile land. A person will harvest only that which he has planted: if good, he will receive good; if evil he will receive evil. Allah says: (And put forward to them the example of the life of this world, it is like the rain which We send down from the sky, and the vegetation of the earth mingles with it, and becomes fresh and green. But [later ] it becomes dry and broken pieces, which the winds scatter. And Allah is Able to do everything. Wealth and children are the adornment of the life of this world. But the good righteous deeds, that last, are better with your Lord for rewards and better in respect of hope.) [ 18:45-46 ]

Allah has clarified to us the reality of the life of this world and has informed us that it is like a fleeting shadow.

Due to the inferiority of this material world, Allah grants it to the disbelievers as well (And [mention ] when Abraham said, “My Lord, make this a secure city and provide its people with fruits - whoever of them believes in Allah and the Last Day.”

Allah said, “And whoever disbelieves - I will grant him enjoyment for a little; then I will force him to the punishment of the Fire, and wretched is the destination.”) [ 2:126 ]

He also says: (To each [category ] We extend - to these and to those - from the gift of your Lord. And never has the gift of your Lord been restricted. Look how We have favored [in provision ] some of them over others. But the Hereafter is greater in degrees [of difference ] and greater in distinction.) [ 17:20-21 ]

Sahl b. Sa’d said: ‘The Messenger of Allah passed through Dhul-Hulaifah and saw a bloated carcass of a sheep, and said: ‘Isn’t this sheep worthless to its master?’ The Companions said: ‘Yes!’ He said: ‘By the one in Whose hands is my soul, this world is far more worthless to Allah than this sheep is to its master. Were this life equal to a wing of a fly, He would not have given the unbeliever even a sip of water.’ [Haakim ]

Allah encourages us to seek the Hereafter and its bounties. He says: (Nay, you prefer the life of this world; Although the Hereafter is better and more lasting.) [ 87:16-17 ]

The Messenger of Allah (s) says: “By Allah, the life of this world compared to the Hereafter is like nothing except the likes of someone who dips his finger into this - and he pointed to the sea - let him see with what he returns with (how much water is on his finger as compared to the sea).” [ Muslim ]

No one will enjoy the bounties of the Hereafter except the best of the creation, those who Allah (y) chose and is pleased with. Allah says: (As for him who gives (in charity) and keeps his duty to Allah and fears Him. And believes in the best [reward]. We will make smooth for him the path of goodness. But he who is a greedy miser and thinks himself self-sufficient. And denies the best [reward]. We will make smooth for him the path for evil.) [ 92:5-10 ]

This does not mean that one must become a monk and leave all the good and permissible things in this life from food, drink, clothes and sex. Allah says: (Say: ‘Who has forbidden the adornment of Allah which He has produced for His servants and the good [lawful ] things of provision?’) [ 7:32 ]

The Messenger of Allah (s) said: “A strong believer is better and more beloved to Allah than a weak believer, and in each one there is good. Be keen to do what benefits you and seek help in Allah, and do not be neglectful in doing so. And if any mishap befalls you, do not say, ‘If only I had done such and such,’ but rather say, ‘This is the decree of Allah, and whatever He Wills He does’, for indeed (the saying of) ‘if’ opens the door for the Devil.” [ Muslim ]

What the Deen commands is that we be moderate in our lifestyles. Allah says: (And let not your hand be tied to your neck, nor stretch it forth to its utmost reach, so that you become blameworthy and in severe poverty. Truly, your Lord enlarges the provision for whom He wills and straitens [for whom He wills]. Verily, He is Ever All- Knower, All-Seer of His slaves.) [ 17:29-30 ]

what is the goal in the creation of humans and jinn ?

Allah created men and jinn to worship Him alone. Allah says: (And I created not the jinn and humans except they should worship Me. I seek not any provision from them nor do I ask that they should feed Me. Verily, Allah is the All- Provider, Owner of Power, the Most Strong.) [ 51:56-58 ]

Man was not created without purpose. Allah says: (Did you think that We created you uselessly and that to Us you would not be returned? So exalted is Allah, the Sovereign, the Truth; there is no deity except Him, Lord of the Noble Throne.) [ 23:115-116 ]
Due to the inferiority of this world, Allah grants it to the disbelievers kuffaar as well as the believers.

No one will enjoy the bounties of the Hereafter except the best of the creation; those that Allah chose.

Allah sent messengers to humanity in different periods of time to clarify to them and guide them to the Straight Path which leads to the Pleasure of Allah. Allah says: (Mankind was [of] one religion [before their deviation]; then Allah sent the prophets as bringers of good tidings and warners and sent down with them the Scripture in truth to judge between the people concerning that in which they differed. And none differed over the Scripture except those who were given it - after the clear proofs came to them - out of jealous animosity among themselves. And Allah guided those who believed to the truth concerning that over which they had differed, by His permission. And Allah guides whom He wills to a straight path.) [2:213]

This was the case until all the messages were completed and finalized by the Message of Muhammad (s) who was sent to mankind at large. Allah says: Say O Muhammad: “Show me those whom you have attached to Him as partners. No! Rather, He [alone ] is Allah, the Exalted in Might, the Wise.”) [ 34:27 ]

The role which humans were created to fulfill is clear and determined: to worship Allah Who created them. Whoever employs his life in that for which he was created will achieve true happiness, even if the joys he possesses of this life are little. Whereas, whoever does not employ his life in that for which he was created will only find loss, psychological problems, unease, and sorrow in this life, even if all the entertainments and joys of this life were made available to him. Allah says: (… then whoever follows My guidance will neither go astray [in the world ] nor suffer [in the Hereafter]. And whoever turns away from My remembrance - indeed, he will have a depressed life, and We will gather him on the Day of Resurrection blind.) [ 20:123-124 ]

Nothing has been created in this universe except for a definite purpose, wisdom and greater benefit, whether we understand it or not. Allah says: (And We created not the heaven and the earth and all that is between them without purpose. That is the consideration of those who disbelieve. Then woe to those who disbelieve from the Fire!) [ 38:27 ]

The worship of Allah is accomplished through fulfilling His commandments and abstaining from His prohibitions, which must be done in accordance to His legislation. Allah says: (And verily, this is my Straight Path, so follow it, and follow not [other ] paths, for they will separate you away from His Path. This He has ordained for you that you may become the pious.) [ 6:153 ]

One must not say about the Deen things which Allah did not legislate, whether willingly or unintentionally. Allah says: (And the Most Beautiful Names belong to Allah, so invoke Him by them. And leave [the company of ] those who practice deviation concerning His names. They will be recompensed for what they have been doing.) [ 7:180 ]