Jazaki Allah khairan sister May Allah open our hearts:
Allah swears by saying:
﴿ وَٱلَّيۡلِ إِذَا يَغۡشَىٰ ﴾
(By the night as it envelops.) meaning, when it covers the creation with its darkness.
﴿ وَٱلنَّہَارِ إِذَا تَجَلَّىٰ ﴾
(By the day as it appears.) meaning, with its light and its radiance.
﴿ وَمَا خَلَقَ ٱلذَّكَرَ وَٱلۡأُنثَىٰٓ ﴾
(By Him Who created male and female.) This is similar to Allah's saying,
﴿ وَخَلَقۡنَـٰكُمۡ أَزۡوَٲجً۬ا ﴾
(And We have created you in pairs.) (78:8) It is also similar to saying,
﴿ وَمِن ڪُلِّ شَىۡءٍ خَلَقۡنَا زَوۡجَيۡنِ ﴾
(And of everything We have created pairs.) (51:49) And just as these things that are being sworn by are opposites, likewise that which this swearing is about are opposing things. This is why Allah says,
﴿ إِنَّ سَعۡيَكُمۡ لَشَتَّىٰ ﴾
(Certainly, your efforts and deeds are diverse.) meaning, the actions of the servants that they have performed are also opposites and diverse. Therefore, there are those who do good and there are those who do evil. Allah then says,
﴿ فَأَمَّا مَنۡ أَعۡطَىٰ وَٱتَّقَىٰ ﴾
(As for him who gives and has Taqwa.) meaning, he gives what he has been commanded to give and he fears Allah in his affairs.
﴿ وَصَدَّقَ بِٱلۡحُسۡنَىٰ ﴾
(And believes in Al-Husna.) meaning, in the compensation for that. This was said by Qatadah. Khusayf said, "In the reward.'' Then Allah says,
﴿ فَسَنُيَسِّرُهُ ۥ لِلۡيُسۡرَىٰ ﴾
(We will make smooth for him the path of ease.) Ibn `Abbas said, "Meaning for goodness.'' Thus, Allah says,
﴿ وَأَمَّا مَنۢ بَخِلَ ﴾
(But he who is greedy) meaning, with that which he has.
﴿ وَٱسۡتَغۡنَىٰ ﴾
(and thinks himself self-sufficient,) `Ikrimah reported that Ibn `Abbas said, "This means he is stingy with his wealth and considers himself to be in no need of his Lord, the Mighty and Majestic.'' This was recorded by Ibn Abi Hatim.
﴿ وَكَذَّبَ بِٱلۡحُسۡنَىٰ ﴾
(And denies Al-Husna.) meaning, the recompense in the abode of the Hereafter.
﴿ فَسَنُيَسِّرُهُ ۥ لِلۡعُسۡرَىٰ ﴾
(We will make smooth for him the path to evil.) meaning, the path of evil. This is as Allah says,
﴿ وَنُقَلِّبُ أَفۡـِٔدَتَہُمۡ وَأَبۡصَـٰرَهُمۡ كَمَا لَمۡ يُؤۡمِنُواْ بِهِۦۤ أَوَّلَ مَرَّةٍ۬ وَنَذَرُهُمۡ فِى طُغۡيَـٰنِهِمۡ يَعۡمَهُونَ ﴾
(And We shall turn their hearts and their eyes away, as they refused to believe therein for the first time, and We shall leave them in their trespass to wander blindly.) (6:110) And there are many Ayat with this meaning, proving that Allah rewards those who intend good with success, while whoever intends evil is abandoned, and all of this is in accordance with a preordained decree. There are also many Hadiths that prove this.
Imam Ahmad recorded from Abu Bakr that he said to the Messenger of Allah, "O Messenger of Allah! Do we act according to what has already been decided, or is the matter just beginning (i.e., still undecided)'' He replied,
« بَلْ عَلَى أَمْرٍ قَدْ فُرِغَ مِنْه »
(Indeed it is according to what has already been decided.) Then Abu Bakr said, "Then what (good) are deeds, O Messenger of Allah'' He replied,
« كُلٌّ مُيَسَّرٌ لِمَا خُلِقَ لَه »
(Everyone will find it easy to do such deeds that will lead him to what he was created for.)
﴿ فَأَمَّا مَنۡ أَعۡطَىٰ وَٱتَّقَىٰ • وَصَدَّقَ بِٱلۡحُسۡنَىٰ • فَسَنُيَسِّرُهُ ۥ لِلۡيُسۡرَىٰ ﴾
(As for him who gives and has Taqwa, and believes in Al-Husna. “We will make smooth for him the path of ease.),” until the Ayah:
﴿ لِلۡعُسۡرَىٰ ﴾
(the path to evil) He (Imam Al-Bukhari) also recorded another similar narration from `Ali bin Abi Talib in which he said, "We were at a funeral in the cemetery of Baqi` Al-Gharqad when the Messenger of Allah came and sat down. So we came and sat around him and he had a stick with him. Then he bowed his head and he began to scratch the ground with his stick. He then said,
« مَا مِنْكُمْ مِنْ أَحَدٍ أَوْ مَا مِنْ نَفْسٍ مَنْفُوسَةٍ إِلَّا كُتِبَ مَكَانُهَا مِنَ الْجَنَّةِ وَالنَّارِ، وَإِلَّا قَدْ كُتِبَتْ شَقِيَّةً أَوْ سَعِيدَة »
(There is not anyone among you -- or is not a single soul (that has been created) -- except that his place has been written in Paradise or in the Fire, and it has been written that he will be miserable or happy.) A man said, "O Messenger of Allah! Should we just depend on what has been written for us and give up performing deeds. For whoever of us is of the people of happiness then he will be of the people of happiness, and whoever among us is of the people of misery then he will be of the people of misery.'' The Prophet replied,
« أَمَّا أَهْلُ السَّعَادَةِ فَيُيَسَّرُونَ لِعَمَلِ أَهْلِ السَّعَادَةِ، وَأَمَّا أَهْلُ الشَّقَاءِ فَيُيَسَّرُونَ إِلَى عَمَلِ أَهْلِ الشَّقَاءِ، ثُمَّ قَرَأَ:
(Those people who are the people of happiness, they will have the deeds of the people of happiness made easy for them. And those people who are the people of misery, they will have the deeds of the people of misery made easy for them.) Then he recited the Ayah:
﴿ فَأَمَّا مَنۡ أَعۡطَىٰ وَٱتَّقَىٰ • وَصَدَّقَ بِٱلۡحُسۡنَىٰ • فَسَنُيَسِّرُهُ ۥ لِلۡيُسۡرَىٰ • وَأَمَّا مَنۢ بَخِلَ وَٱسۡتَغۡنَىٰ ﴾
﴿ وَكَذَّبَ بِٱلۡحُسۡنَىٰ • فَسَنُيَسِّرُهُ ۥ لِلۡعُسۡرَىٰ ﴾
(As for him who gives and has Taqwa, and believes in Al-Husna. We will make smooth for him the path of ease (goodness). But he who is greedy and thinks himself self-sufficient, and belies Al-Husna. We will make smooth for him the path to evil.)) The other compilers of the Group have also recorded this Hadith.
﴿ إِنَّ عَلَيۡنَا لَلۡهُدَىٰ • وَإِنَّ لَنَا لَلۡأَخِرَةَ وَٱلۡأُولَىٰ • فَأَنذَرۡتُكُمۡ نَارً۬ا تَلَظَّىٰ • لَا يَصۡلَٮٰهَآ إِلَّا ٱلۡأَشۡقَى • ٱلَّذِى كَذَّبَ وَتَوَلَّىٰ • وَسَيُجَنَّبُہَا ٱلۡأَتۡقَى • ٱلَّذِى يُؤۡتِى مَالَهُ ۥ يَتَزَكَّىٰ • وَمَا لِأَحَدٍ عِندَهُ ۥ مِن نِّعۡمَةٍ۬ تُجۡزَىٰٓ • إِلَّا ٱبۡتِغَآءَ وَجۡهِ رَبِّهِ ٱلۡأَعۡلَىٰ • وَلَسَوۡفَ يَرۡضَىٰ ﴾
(12. Truly, on Us is (to give) guidance.) (13. And truly, unto Us (belong) the last (Hereafter) and the first (this world).) (14. Therefore I have warned you of a Fire Talazza.) (15. None shall enter it save the most wretched.) (16. Who denies and turns away.) (17. And those with Taqwa will be far removed from it.) (18. He who gives of his wealth for self-purification.) (19. And who has (in mind) no favor from anyone to be paid back.) (20. Except to seek the Face of his Lord, the Most High.) (21. He, surely, will be pleased.)
(copied briefly from tafseer ibn katheer )