In Surah Baqarah, after the introductory passages about different types of people (believers, disbelievers, and hypocrites), Allah gives a general call to Islam to mankind.
In five verses (2:21-25), Allah calls people to Islam and gives proof for God, proof for the Prophet (SAW), warning of punishment, and promise of reward.
In blue is the translation of the Quran, and in black are my words.
1. Worship Allah
Allah says: O mankind, worship your Lord, whom you know exists and deserves worship because He is the one who created you and those before you so that you might be righteous.
How can you deny Him or His blessings when He is the one who:
1) made for you the earth a bed,
2) and made for you the sky a ceiling,
3) and sent down rain from the sky
4) and brought forth fruits from it as food for you.
All of it: the sky, the earth, what comes from the sky, and what comes from the earth comes from Allah Himself.
So do not attribute to Allah equals while you know that He is the true giver of blessings. How can you worship others when they do not deserve it and gave you nothing? How can you worship others when you see this consistent universe that indicates it must have one creator?
2. Follow the Prophet Muhammad (SAW)
Allah says: After believing in Me, believe in this message I have sent down. And if you are in doubt about what We have sent down upon Our Servant [Muhammad] i.e. this Quran, then produce a surah like it if you claim it is possible for a human to invent it.
And call upon your witnesses other than Allah to help you in this task of producing a Surah like it, if you are truthful in the claim that this is man-made. If one man who was never a poet can make it, then so can a group of people who are challenged and can collaborate as much as they want.
But if you do not make a surah like it to prove this can be man-made – and you will never be able to as this Quran is miraculous and clearly not man-made – then believe in Islam and fear the Fire, whose fuel is men and stones. It is prepared for the disbelievers if they still disbelieve after this clear sign.
And give good tidings to those who believe after this sign and do righteous deeds that they will have gardens [in Paradise] beneath which rivers flow.
This is reward to motivate them. To mention just one of the many amazing things in Paradise: Whenever they are provided with some fruit from it, they will say, “This is what we were provided with before.” Even though they were only given something similar to the fruits they used to have in the world. Everything good you have in this world will be even better in Paradise. This world is nothing but a demo for what awaits in Paradise.
And they will also have purified spouses in it, and they will abide in it eternally.