In the books of history, it is written that the very first mention of a large flag being used was during the Battle of Khaybar. Prior to that there was only use of smaller flags. Buraidah al-Aslami narrates that when the Holy Prophet (sa) reached the battlefield of Khaybar, he handed the flag to Hazrat Umar (ra) bin al-Khattab.
There are further details of this in the books of history. It is recorded that the very first mention of a large flag being used was during the Battle of Khaybar. Prior to that there was only use of small flags. The flag of the Holy Prophet (sa) which was made from a cloth of Hazrat Aishahra, the Mother of the Believers, was black and it was named Uqab. The Holy Prophet (sa) also had a white flag, which he handed to Hazrat Ali (ra).
There was mention previously of a black flag which was made from a cloth of Hazrat Aishahra and then there is mention of this white flag which was given to Hazrat Ali (ra). The Holy Prophet (sa) handed one of the flags to Hazrat Hubbabra bin Munzir and the other to Hazrat Saad (ra) bin Ubadah. When the Holy Prophet (sa) reached Khaybar, he was suffering from a severe migraine and was unable to go out. On this occasion, he initially handed his flag to Hazrat Abu Bakr (ra), then he handed the same one to Hazrat Umar (ra). That day, a fierce battle ensued and the Muslims were unable to penetrate the fortress. The Holy Prophet (sa) said, “Tomorrow I shall grant my flag to the one through whom Allah the Almighty shall grant us victory.” The following day the Holy Prophet (sa) gave that flag to Hazrat Ali (ra), and at his hands, God Almighty did indeed grant them victory.
(Subul Al-Huda Wa Al-Rishad, Vol. 5, p. 120, 124, 125, Dar-ul-Kutub al-Ilmiyyah, Beirut, 1993)
Ibn Ishaq says that he asked Ibn Shihab Zuhri that what were the conditions stipulated by Holy Prophet (sa) upon which he gave the date fields of Khaybar to the Jews. Zuhri replied that after the battle, the Holy Prophet (sa) gained victory over Khaybar and Khaybar itself was among the spoils of war which God Almighty granted to the Holy Prophet (sa). A fifth of this belonged to the Holy Prophet (sa), which he distributed amongst the Muslims.
The Jews who were prepared to be expelled from their lands after the battle came down from their fortresses. The Holy Prophet (sa) called them and said:
“If you so wish this wealth can be given to you, upon the condition that you work therein and distribute its fruits between us and yourselves. There will be a division of the produce and if you so wish to remain here then I shall grant you a place to stay where God Almighty wills for you to stay.”
So the Jews accepted this offer and continued working in these fields. The Holy Prophet (sa) would send Hazrat Abdullah (ra) bin Rawahah to distribute the fruits from these fields and he would equitably act when assessing how much share would be given to the Jews. It was not the case that he would keep the good fruit for the Muslims; rather, the division would be in accordance with justice. Then, when God Almighty decreed for the demise of the Holy Prophet (sa), Hazrat Abu Bakr (ra) continued the same treatment with the Jews that was afforded to them by the Holy Prophet (sa).
In the beginning of his Khilafat, Hazrat Umar (ra) also continued this treatment, but then he heard what the Holy Prophet (sa) said in his final illness before his demise that two religions would not coexist in the Arab lands.
Hazrat Umar (ra) investigated this further and when this saying was proven true, he wrote to the Jews of Khaybar stating:
“God Almighty has decreed for you to be expelled. I received news that the Holy Prophet (sa) said that two religions would not coexist in the Arab lands. Hence, those Jews who had an agreement with the Holy Prophet (sa) should come to me so that I may honour it. But those who do not have an agreement shall prepare to be exiled.”
In other words, if anyone had an agreement with the Holy Prophet (sa), they could remain and he would honour that agreement with them. But if anyone did not have such an agreement, they would have to leave their land. Therefore, Hazrat Umar (ra) exiled those who had no agreement with the Holy Prophet (sa).
Hazrat Abdullah (ra) bin Umar says:
“I went with Hazrat Zubair (ra) bin al-Awwam and Hazrat Miqdad (ra) bin Aswad to see our property in Khaybar. When we reached, we spilt up in order to go and see our respective properties. At night, I was attacked whilst I was asleep. My joints at the elbows were dislocated. In the morning, two companions of mine came screaming as they approached me. They asked who did this to me. I told them that I did not know. They both then fixed my arms and brought me to Hazrat Umar (ra). Hazrat Umar (ra) stated that this was the work of the Jews. Hazrat Umar (ra) then stood to address the people, saying, ‘O people, the Holy Prophet (sa) stipulated a condition with the Jews that we would exile them whenever we pleased. Now the Jews have attacked Hazrat Abdullah (ra) bin Umar and dislocated the joints of his elbows, as you will now have come to know. Prior to this, they had also attacked an Ansari and I have no doubt that these people are their accomplices. We have no enemy other than them so if anyone has any wealth there should safeguard it, for I am about to expel the Jews from there.” Subsequently, he expelled the Jews.
Abdullah bin Muqnaf relates that when Hazrat Umar (ra) expelled the Jews from Khaybar, he himself rode with the Muhajireen and the Ansar. Hazrat Jabbar (ra) bin Sakhr and Hazrat Yazid (ra) bin Thabit also accompanied them as they went forth. Hazrat Jabbar (ra) was the one who assessed the fruits for the people of Medina and was responsible for keeping their account for them. Both of them divided [the fruits] between the people of Khaybar according to the standard set from before.
(Sirat ibn Hisham, p. 710, Dar-ul-Kutub al-Ilmiyyah, Beirut, 2001)
Then, there is the incident of Hazrat Hatib (ra) who secretly sent a woman with a letter to the idolaters of Mecca, which contained some plans of the Holy Prophet (sa). The Holy Prophet (sa) received news of this from Allah the Almighty and so he sent Hazrat Ali (ra) [to retrieve it]. That lady was intercepted along the way.
Afterwards, when the Holy Prophet (sa) asked Hatib [why he had done this], Hatib presented his reason and said that his faith had not faltered at all, in fact he had firm faith. Hazrat Hatib (ra) assured the Holy Prophet (sa) of this and the Holy Prophet (sa) accepted it; however, Hazrat Umar (ra) submitted, “O Messenger (sa) of Allah, allow me to sever the head of this hypocrite.” The Holy Prophet (sa) said, “He [Hatib] took part in the Battle of Badr and you may not be aware of the fact that Allah has looked upon those who took part in Badr and said, ‘You may do as you please, for I have covered your sins and overlooked them.’”
(Sahih Bukhari, Kitab-ul-Maghazi, Baab Ghazwah Al-Fath, Hadith no. 4274)