(And don't be weak in the pursuit of the enemy;) means, do not weaken your resolve in pursuit of your enemy. Rather, pursue them vigorously, fight them and be wary of them.
(if you are suffering then surely they are suffering as you are suffering,) meaning, just as you suffer from injuries and death, the same happens to the enemy. In another Ayah, Allah said,
(If you suffer a harm, be sure a similar harm has struck the others). Allah then said,
(but you have a hope from Allah that for which they hope not;) meaning, you and they are equal regarding the injuries and pain that you suffer from. However, you hope for Allah's reward, victory and aid, just as He has promised you in His Book and by the words of his Messenger . Surely, Allah's promise is true. On the other hand, your enemies do not have hope for any of this. So, it is you, not they, who should be eager to fight so that you establish the Word of Allah and raise it high.
(And Allah is Ever All-Knowing, All-Wise.) means, He is most knowledgeable and wise in all what He decides, decrees, wills and acts on concerning various worldly and religious ordainments, and He is worthy of praise in all conditions.
(105. Surely, We have sent down to you (O Muhammad ) the Book in truth that you might judge between men by that which Allah has shown you, so be not a pleader for the treacherous.) (106. And seek the forgiveness of Allah, certainly, Allah is Ever Oft-Forgiving, Most Merciful.) (107. And argue not on behalf of those who deceive themselves. Verily, Allah does not like anyone who is a betrayer, sinner.) (108. They may hide (their crimes) from men, but they cannot hide (them) from Allah; for He is with them (by His knowledge), when they plot by night in words that He does not approve. And Allah ever encompasses what they do.) (109. Lo! You are those who have argued for them in the life of this world, but who will argue for them on the Day of Resurrection against Allah, or who will then be their defender)
Allah says to His Messenger, Muhammad ,
(Surely, We have sent down to you the Book in truth) meaning, it truly came from Allah and its narrations and commandments are true. Allah then said,
(that you might judge between men by that which Allah has shown you,) In the Two Sahihs, it is recorded that Zaynab bint Umm Salamah said that Umm Salamah said that the Messenger of Allah heard the noise of disputing people close to the door of his room, and he went out to them saying,
(Verily, I am only human and I judge based on what I hear. Some of you might be more eloquent in presenting his case than others, so that I judge in his favor. If I judge in one's favor concerning the right of another Muslim, then it is a piece of the Fire. So let one take it or leave it.) Imam Ahmad recorded that Umm Salamah said, "Two men from the Ansar came to the Messenger of Allah with a dispute regarding some old inheritance, but they did not have evidence. The Messenger of Allah said,
(You bring your disputes to me, but I am only human. Some of you might be more persuasive in their arguments than others. I only judge between you according to what I hear. Therefore, whomever I judge in his favor and give him a part of his brother's right, let him not take it, for it is a part of the Fire that I am giving him and it will be tied around his neck on the Day of Resurrection.) The two men cried and each one of them said, `I forfeit my right to my brother.' The Messenger of Allah said,
(Since you said that, then go and divide the inheritance, and try to be just in your division. Then draw lots, and each one of you should forgive his brother thereafter (regardless of who got the best share).)'' Allah's statement,
(They may hide (their crimes) from men, but they cannot hide (them) from Allah;) chastises the hypocrites because they hide their evil works from the people so that they will not criticize them. Yet, the hypocrites disclose this evil with Allah, Who has perfect watch over their secrets and knows what is in their hearts. This is why Allah said,
(for He is with them (by His knowledge), when they plot by night in words that He does not approve. And Allah ever encompasses what they do) threatening and warning them. Allah then said,
(Lo! You are those who have argued for them in the life of this world,) meaning, suppose these people gain the verdict from the rulers in their favor in this life, since the rulers judge according to what is apparent to them. However, what will their condition be on the Day of Resurrection before Allah, Who knows the secret and what is even more hidden Who will be his advocate on that Day Verily, none will support them that Day. Hence, Allah's statement,
(or who will then be their defender)
(110. And whoever does evil or wrongs himself but afterwards seeks Allah's forgiveness, he will find Allah Oft-Forgiving, Most Merciful.) 111. And whoever earns sin, he earns it only against himself. And Allah is Ever All-Knowing, All-Wise.) (112. And whoever earns a fault or a sin and then blames it on someone innocent, he has indeed burdened himself with falsehood and a manifest sin.) (113. Had not the grace of Allah and His mercy been upon you, a party of them would certainly have made a decision to mislead you, but they mislead none except their own selves, and no harm can they do to you in the least. Allah has sent down to you the Book, and the Hikmah, and taught you that which you knew not. And ever great is the grace of Allah unto you.)