Quran

(Thus We have tested some of them by means of others), We tested the disbelievers by the believers, and that was when the disbelievers said: "are these poor slaves chosen by Allah over us for truth and eternal bliss while we are the noble rich?" They were dismissing this notion! So, Allah responded to them saying: (Does Allah not know best those who are grateful). Ibn Juzay: 1/271.
Question: The guidance of poor slaves was a test for the disbelievers. How?

The "grateful" are those who appreciate the blessing of faith in Allah, and offer their gratitude to Him for that. Ibn Taimyah: 3/28.
Question: What is meant by the "grateful" in this verse?

Meaning: When the believers come to you, greet them and welcome them warmly, and say things to raise their morale and motivate them, tell them of the mercy, bounty and kindness of Allah, and encourage them by all means that may achieve that; and warn them against committing sins and persisting therein, and instruct them to repent from sins, so that they may attain the forgiveness and bounty of their Lord. Al-Saadi: 258.
Question: How should the scholars and preachers deal with their righteous followers?

When the way of evildoers becomes known, then the way of the believers are also known. Al-Qurtubi: 8/396.
Question: Allah mentions the way of the evildoers and not that of the believers. Why ?

Once the way of the evildoers is made clear, it can be avoided, unlike when it remains indistinct and ambiguous, in which case this noble goal [of avoiding it] cannot be attained. Al-Saadi: 258.
Question: What is the wisdom behind clarifying the ways of the evildoers?

Meaning: I would have brought it upon you and there would be nothing good for you in that, but the matter is in the Hand of the Most Forbearing, Most Patient, Whom people disobey in the most audacious manner, yet He grants them well-being and provision, and bestows His blessings, both apparent and hidden, upon them. Al-Saadi: 259.
Question: This verse describes the great mercy of Allah, the Almighty, how?

(And not a leaf falls but that He knows it), Allah knows when and where a tree leaf falls, and how long it stays airborne before reaching the ground. He knows when every grain will grow, how much it will grow and who will eat from it. Al-Qurtubi: 8/405.
Question: This verse states an example of the limitless knowledge of Allah. Explain.