The verses:  

In the name of Allah, the Most Beneficent, the Most Merciful.

Almighty Allah Says (what means): "When the victory of Allah has come and the conquest [of Makkah]. And you see the people entering into the religion of Allah in multitudes. Then exalt [Him] with praise of your Lord and ask forgiveness of Him. Indeed, He is ever Accepting of repentance." [Quran: 110:1-4]

Explanation:

Imaam At-Tirmithi related from Anas Ibn Maalik may Allah be pleased with him that the Messenger  once asked a man: "Are you married?" He replied: "No, I swear by Allah, O Messenger of Allah! For I have nothing, so how can I marry?" He asked the man: "Do you not have: "Say: `He is Allah, the One."'[i.e., Soorah Al-Ikhlaas]?" The man replied: "Certainly!" He said: "It is (equivalent to) one third of the Quran." Then he asked: "Do you not have: "When the victory of Allah has come and the conquest [of Makkah]" [i.e., Soorah An-Nasr]?" The man replied: "Certainly!" The Prophet then said: "It is (equivalent to) one quarter of the Quran."

`Ubaydullaah Ibn `Abdullaah Ibn `Utbah may Allah be pleased with him narrated that Ibn `Abbaas may Allah be pleased with him said to him: "Do you know which Soorah (chapter) was the last to be revealed from the Quran?" I replied: "Yes, and it was (what means): "When the victory of Allah has come and the conquest [of Makkah]."" He said: "You are right."

Abu Bakr Al-Bazzaar and Al-Bayhaqi both narrated from Ibn `Umar may Allah be pleased with him that he said: "This Soorah was revealed to the Messenger of Allah during the days of Tashreeq (i.e., the 11th, 12th and 13th of Thu'l-Hijjah) and he knew that it was his farewell address. He called for his riding-camel, and when he had travelled some way on it, he stood and addressed the people with his famous farewell speech. According to Imaam Al-Bayhaqi Ibn `Abbaas may Allah be pleased with him said: "This Soorah was revealed, following which the Messenger of Allah summoned his daughter Faatimah may Allah be pleased with her and said to her: "It heralds my death." At this, Faatimah may Allah be pleased with her began to cry; but she laughed when he said: "Have Patience, for you are the first of my family who will join me."  [Muslim]

Imaam At-Tabaraani related on the authority of Ibn `Abbaas may Allah be pleased with him that he said: "When the Soorah: "When the victory of Allah has come and the conquest [of Makkah]." was revealed, it heralded to Allah's Messenger that his death was near, and so he intensified his preparations for the Hereafter (by increasing his prayers, fasting, supplicating etc.); after embarking upon this, he said: "The conquest and the help of Allah have come, and the people of Yemen have come." A man asked: "O Messenger of Allah! Who are the people of Yemen?" He replied: "A people who are gentle-hearted and moderate in their ways: faith is in Yemen; fiqh (understanding of Islam) is in Yemen." [Al-Bukhari]

It has been confirmed from Ibn `Abbaas may Allah be pleased with him that the Messenger of Allah said on the day of the conquest of Makkah: "There is no Hijrah (i.e. emigration) after the conquest, but there is Jihaad and Niyyah (pure intention) and if you are called upon, then respond to the call." [Al-Bukhari & Muslim]

Masrooq may Allah be pleased with him said: "I heard `Aa'ishah may Allah be pleased with her saying that the Messenger of Allah would repeat: "Glorified be Allah and all praise be to Him, I ask Allah's forgiveness and I turn to Him in repentance."  He continued: "Indeed, my Lord has informed me that I will see a sign amongst my people, and He ordered me, if I do see it, to glorify His praises and ask His forgiveness, and I have seen it, (it is): 'When the victory of Allah has come and the conquest [of Makkah]. And you see the people entering into the religion of Allah in multitudes. Then exalt [Him] with praise of your Lord and ask forgiveness of Him. Indeed, He is ever Accepting of repentance.'"" [Muslim]

Umm Salamah may Allah be pleased with her said: "Towards the end of his life, the Messenger of Allah would not stand, nor sit, nor depart, nor arrive, without saying: "Most Glorified is Allah and all praise is due to Him." So I said to him: "O Messenger of Allah! I have observed you frequently glorifying Allah and praising Him." He said: "I was ordered to do it."  Then he said: "When the victory of Allah has come and the conquest [of Makkah]..." (to the end of the Soorah)." What is meant by 'the conquest' is the conquest of Makkah. The people of Arabia were slow in answering the call to Islam until the fall of Makkah, then they entered the Religion of Allah in crowds and within two years, the whole of Arabia became unified in faith and all the tribes of Arabia embraced Islam.

Imaam Al-Bukhari reported that when Makkah was conquered, delegations from all the tribes of Arabia came to the Messenger of Allah to declare their allegiance to Islam, while prior to it, they were slow to embrace Islam.

Imam Ahmad narrated on the authority of the neighbour of Jaabir Ibn `Abdullaah may Allah be pleased him that he (i.e., the neighbour) said: "I once returned from a journey and Jaabir Ibn `Abdullaah came to me and greeted me. I began to talk with him about the disunity of the people and their innovations (in religion). Jaabir then began to cry and said: "I heard Allah's Messenger say: "Indeed, the people entered the Religion of Allah in crowds and they will abandon it in crowds."

From: Tafseer Ibn Katheer – 'Juz' 'Amma'