Allah's Messenger (ﷺ) saw him (i.e. Ka'b) while the lice were falling on his face.

(Reporting the speech of Ka`b bin Umra) Allah's Messenger (ﷺ) saw him (i.e. Ka`b) while the lice were falling on his face. He asked (him), "Have your lice troubled you?" He replied in the affirmative. So, he ordered him to get his head shaved while he was at Al-Hudaibiya. At that time they were not permitted to finish their Ihram, and were still hoping to enter Mecca. So, Allah revealed the verses of Al-Fidya. Allah's Messenger (ﷺ) ordered him to feed six poor persons with one Faraq of food or to slaughter one sheep (as a sacrifice) or to fast for three days.

I sat with Ka`b bin 'Ujra and asked him about the Fidya. He replied, "This revelation was revealed concerning my case especially, but it is also for you in general. I was carried to Allah's Messenger (ﷺ) and the lice were falling in great number on my face. The Prophet (ﷺ) said, "I have never thought that your ailment (or struggle) has reached to such an extent as I see. Can you afford a sheep?" I replied in the negative. He then said, "Fast for three days, or feed six poor persons each with half a Sa of food." (1 Sa = 3 Kilograms approx.)

While I was going to help this man ('Ali Ibn Abi Talib), Abu Bakra met me and asked, "Where are you going?" I replied, "I am going to help that person." He said, "Go back for I have heard Allah's Messenger (ﷺ) saying, 'When two Muslims fight (meet) each other with their swords, both the murderer as well as the murdered will go to the Hell-fire.' I said, 'O Allah's Messenger (ﷺ)! It is all right for the murderer but what about the murdered one?' Allah's Messenger (ﷺ) replied, "He surely had the intention to kill his companion."

Allah's Messenger (ﷺ) was prevented from performing (`Umra) Therefore, he shaved his head and had sexual relations with his wives and slaughtered his Hadi and performed Umra in the following year.

Some of the sons of `Abdullah told him (i.e. `Abdullah) if he had stayed (and not performed Hajj that year).

That Ubaidullah bin `Abdullah and Salim bin `Abdullah informed him that they told Ibn `Umar when Ibn Az-Zubair was attacked by the army, saying "There is no harm for you if you did not perform Hajj this year. We are afraid that you may be prevented from reaching the Ka`ba." Ibn `Umar said "We set out with Allah's Messenger (ﷺ) and the non-believers of Quraish prevented us from reaching the Ka`ba, and so the Prophet (ﷺ) slaughtered his Hadi and got his head shaved." Ibn `Umar added, "I make you witnesses that I have made `Umra obligatory for me. And, Allah willing, I will go and then if the way to Ka`ba is clear, I will perform the Tawaf, but if I am prevented from going to the Ka`ba then I will do the same as the Prophet (ﷺ) did while I was in his company." Ibn `Umar then assumed Ihram for Umra from Dhul-Hulaifa and proceeded for a while and said, "The conditions of `Umra and Hajj are similar and I make you witnesses that I have made `Umra and Hajj obligatory for myself." So, he did not finish the Ihram till the day of Nahr (slaughtering) came, and he slaughtered his Hadi. He used to say, "I will not finish the Ihram till I perform the Tawaf, one Tawaf on the day of entering Mecca (i.e. of Safa and Marwa for both `Umra and Hajj).

When `Abdullah bin `Umar set out for Mecca intending to perform Umra, at the time of afflictions, he said, "If I should be prevented from reaching the Ka`ba, then I would do the same as Allah's Messenger (ﷺ) did, so I assume the lhram for Umra as Allah's Messenger (ﷺ) assumed the Ihram for Umra in the year of Hudaibiya."

I was with Ibn `Umar on the way to Mecca, and he got the news that Safiya bint Abu Ubaid was seriously ill. So, he hastened his pace, and when the twilight disappeared, he dismounted and offered the Maghrib and `Isha' prayers together. Then he said, "I saw that whenever the Prophet (ﷺ) had to hasten when traveling, he would delay the Maghrib prayer and join them together (i.e. offer the Maghrib and the `Isha prayers together).

The Prophet (ﷺ) said, "Traveling is a kind of torture as it prevents one from eating, drinking and sleeping properly. So, when one's needs are fulfilled, one should return quickly to one's family."