In The Name of Allaah, The Most Merciful, The Bestower of Mercy
Allaah (The Most High) said:
الٓرۚ ڪِتَـٰبٌ أَنزَلۡنَـٰهُ إِلَيۡكَ لِتُخۡرِجَ ٱلنَّاسَ مِنَ ٱلظُّلُمَـٰتِ إِلَى ٱلنُّورِ بِإِذۡنِ رَبِّهِمۡ إِلَىٰ صِرَٲطِ ٱلۡعَزِيزِ ٱلۡحَمِيدِ
ٱللَّهِ ٱلَّذِى لَهُ ۥ مَا فِى ٱلسَّمَـٰوَٲتِ وَمَا فِى ٱلۡأَرۡضِۗ وَوَيۡلٌ۬ لِّلۡكَـٰفِرِينَ مِنۡ عَذَابٍ۬ شَدِيدٍ
ٱلَّذِينَ يَسۡتَحِبُّونَ ٱلۡحَيَوٰةَ ٱلدُّنۡيَا عَلَى ٱلۡأَخِرَةِ وَيَصُدُّونَ عَن سَبِيلِ ٱللَّهِ وَيَبۡغُونَہَا عِوَجًاۚ أُوْلَـٰٓٮِٕكَ فِى ضَلَـٰلِۭ بَعِيدٍ۬
Alif-Lam-Ra. [These letters are one of the miracles of the Qur’an, and none but Allah (Alone) knows their meanings]. (This is) a Book which We have revealed unto you (O Muhammad ) in order that you might lead mankind out of darkness by their Lord’s Leave to the Path of the All-Mighty, the Owner of all Praise. Allah to Whom belongs all that is in the heavens and all that is in the earth! And woe unto the disbelievers from a severe torment. Those who prefer the life of this world instead of the Hereafter, and hinder (men) from the Path of Allah (i.e. Islam) and seek crookedness therein – They are far astray.
[الٓرۚ ڪِتَـٰبٌ أَنزَلۡنَـٰهُ إِلَيۡكَ لِتُخۡرِجَ ٱلنَّاسَ مِنَ ٱلظُّلُمَـٰتِ إِلَى ٱلنُّورِ بِإِذۡنِ رَبِّهِم]
Alif-Lam-Ra. (This is) a Book which We have revealed unto you (O Muhammad) in order that you might lead mankind out of darkness by their Lord’s Leave”
Imaam Shanqeetee (rahimahullaah) said:
Allaah (The Most High) clarified in this noble ayah that He sent down this great Book unto His Prophet (sallal-laahu-alayhi-wasallam) in order that he may remove mankind from the darkness of disbelief and misguidance and (enter them) into the light of Imaan and guidance. The meaning of this ayah has been made clear in other Aayaat, such as the saying of Allaah:
[هُوَ ٱلَّذِى يُنَزِّلُ عَلَىٰ عَبۡدِهِۦۤ ءَايَـٰتِۭ بَيِّنَـٰتٍ۬ لِّيُخۡرِجَكُم مِّنَ ٱلظُّلُمَـٰتِ إِلَى ٱلنُّورِۚ]
It is He Who sends down manifest Ayat (proofs, evidences, verses, lessons, signs, revelations, etc.) to His slave (Muhammad) that He may bring you out from darkness into light.
[Soorah Hadeed. Ayah: 9]
Indeed, Allaah (The Most High) clarified in this ayah (i.e. 14:1) that none can be removed from darkness and (entered) into light except by His Leave, as He stated: [بِإِذۡنِ رَبِّهِم – By their Lord’s Leave]. This has been made clear in other Aayaat, such as the saying of Allaah: [وَمَآ أَرۡسَلۡنَا مِن رَّسُولٍ إِلَّا لِيُطَاعَ بِإِذۡنِ ٱللَّهِۚ – We sent no Messenger, but to be obeyed by Allah’s Leave]
[Nisaa. Ayah 64]
Also the saying of Allaah: [وَمَا كَانَ لِنَفۡسٍ أَن تُؤۡمِنَ إِلَّا بِإِذۡنِ ٱللَّهِۚ –It is not for any person to believe, except by the Leave of Allaah] [Yoonus. Ayah 100] 
Imaam Sadi (rahimahullaah) said:
Allaah (The Most High) informed (us) that He revealed His Book unto His Messenger Muhammad (sallal-laahu-alayhi-wasallam) for the benefit of the creation (i.e. Mankind and Jinn); so that they might be removed from the darkness of ignorance, disbelief, evil manners and all types of disobedience, (and entered into) the light of knowledge, Imaan and good manners.
And concerning the statement of Allaah: [بِإِذۡنِ رَبِّهِم – By their Lord’s Leave]; that is they cannot reach the goal of that which is pleasing to Allaah, except by Allaah’s Will and Help. So in this there is an exhortation for the slaves to seek help from their Lord.
Then Allaah explained (the meaning of the) light to which this Book guides to, saying:
[إِلَىٰ صِرَٲطِ ٱلۡعَزِيزِ ٱلۡحَمِيد – To the Path of the All-Mighty, the Owner of all Praise]; that is the path that leads to (obedience to Allaah and His Messenger, success in this life and the next etc) and the abode of honour (i.e. paradise), which (is achieved by way) of having knowledge of the truth and acting upon it. And with regards to the statement: [ٱلۡعَزِيزِ ٱلۡحَمِيدِ – The All-Mighty, the Owner of all Praise] after the mention of the path leading to Him, in this is an indication that the one who follows the straight path is given might by Allaah and he is a strong person, even if there are no helpers for him except Allaah. He is praiseworthy in his affairs and will achieve a good end.
This also indicates that Allaah’s path is the greatest proof that He (The Most High) possesses Perfect Attributes and Lofty Descriptions, and that what He has appointed for His slaves is mighty authority. He is praised in His Statements, Actions and Rulings (i.e. because He is the Bestower of all things and He is free from all imperfections). He alone is described with all the perfect Names and Attributes; He is the only one worthy of worship through those acts of worship (He has prescribed), which are the dignified signposts of the straight path. And just as He is the owner of the kingdom of the heavens and the earth-The Creator, The Sustainer, The Controller of the affairs of the universe- likewise, He has religious rulings for His slaves because He is their Owner (i.e. the Owner of mankind and jinn), and it does not befit His (Wisdom, Majesty, Glory etc) that He leaves them Suda [neglected without being punished or rewarded for the obligatory duties enjoined by Him]
After Allaah clarified the evidences and proofs, He then made a promise to the one who does not pay attention to (such proofs and evidences), saying: [وَوَيۡلٌ۬ لِّلۡكَـٰفِرِينَ مِنۡ عَذَابٍ۬ شَدِيد – And woe unto the disbelievers from a severe torment].
Then Allaah described them, saying: [ٱلَّذِينَ يَسۡتَحِبُّونَ ٱلۡحَيَوٰةَ ٱلدُّنۡيَا عَلَى ٱلۡأَخِرَةِ – Those who prefer the life of this world instead of the Hereafter]. They make it a duty and are satisfied with it, whilst being heedless of the afterlife. [وَيَصُدُّونَ – And they hinder] mankind [ عَن سَبِيلِ ٱللَّهِ– From the Path of Allaah] which Allaah has appointed for His slaves, clarified in His Books and conveyed through the speech of His Messengers. So, these people have indeed turned away from their Protector through enmity and waging war against Him. [وَيَبۡغُونَہَا عِوَجًاۚ – And seek crookedness therein (i.e. in Allaah’s Religion)]; that is: They are eager to ridicule and make it look repugnant, in order to make people flee from it; however Allaah will not allow that to happen, rather He made His religion uppermost even though the disbelievers may hate it.  They desire that Allaah’s path should become crooked, swaying towards (corruption) and deviated from the right course, even though it is self-evident and neither can it be harmed by the one who opposes it nor by the one who forsakes it.  So with this desire of theirs, they are in ignorance and straying far away from the truth and rectification. 
[أُوْلَـٰٓٮِٕكَ فِى ضَلَـٰلِۭ بَعِيدٍ – They are far astray] because they are misguided and misguiding others. They oppose Allaah and His Messenger, and wage war against them; so what type of misguidance can be farther than this? As for the people of Imaan, they are the opposite of these ones–they believe in Allaah and His Aayaat; they prefer the afterlife over the worldly life and call to the path of Allaah. They perfect their actions to the best of their ability and manifest their steadfastness. 
 Abridged: See Tafseerul Qur’aan Bil-Qur’aan Min Adwaa Al-Bayaan.
[2 & 5] Abridged and slightly paraphrased. For further details, see Tayseer Al-Kareem Ar-Rahmaan Fee Tafseer Kalaam Al-Mannaan’ of Imaam Sadi (rahimahullaah)]
 Qurratul Ainayn Alaa Tafseer Al-Jalaalayn
 Al-Misbaah Al-Muneer Fee Tahdheeb Tafseer Ibn Katheer