´Narrated Anas bin Malik:` "My paternal uncle was absent from the fighting of Badr, so he said: 'I was absent from the first fight the Messenger of Allah (ﷺ) fought with idolaters, so if Allah grants me to participate in a fight with the idolaters, then Allah will see what I will do!' So on the Day of Uhud, when the Muslims were driven back he said: 'O Allah! Indeed I am innocent before you of what these people - meaning the idolaters - have done, and I beg of You to excuse these people for what they have done - meaning the Companions. Then he went forward and met up with Sa'd. He said: 'O my brother! Whatever you do, I am with you!' But he was not able to do the same as him. He was found with more than eighty wounds, between blows with the sword, thrusts of a spear, or arrow wounds. We would say: 'It was about him and his companions that (the following) was revealed: 'Of them some have fulfilled their vow, and some of them are still waiting, but they have never changed in the least (33:23). (One of the narrators) Yazid said: "Meaning this Ayah."
Hadith Referenceسنن ترمذي / كتاب تفسير القرآن عن رسول الله صلى الله عليه وسلم / 3201
´Narrated Anas:` "My paternal uncle Anas bin An-Nadr - after whom I was named - did not participate in the battle of Badr with the Messenger of Allah (ﷺ). This distressed him and he said: 'I was absent from the first battle which the Messenger of Allah (ﷺ) attended. By Allah! If Allah gives me the opportunity to participate in another battle along with the Messenger of Allah (ﷺ), then Allah will see what I will do!'" He said: "He did not want to say more than that. A year later, he attended the battle of Uhud, where he saw Sa'd bin Mu'adh and said: 'O Abu 'Amr where are you going?' He said: 'I long for the fragrance of Paradise and I have found it near the mountains of Uhud.' He fought them until he was killed. They found more than eighty wounds on his body, be they from blows of a sword, puncture wounds, or arrows. My paternal aunt Ar-Ruba'i bin An-Nadr said: 'I could not recognize my brother except by his finger tips.' And this Ayah was revealed: 'Among the believers are men who have been true to their covenant with Allah; of them some have fulfilled their vow, and some of them are still waiting, but they have never changed in the least (33:23).'"
Shaykh Dr. Abdur Rahman Freywai
Explanation: 1: Among the believers are such people who fulfilled the promises they made with Allah. Some of them have passed away, and some are waiting for death. They did not make any change in this—that is, in their covenant made with Allah—of any kind (al-Ahzab: 23).
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 3200