Irbad bin Sariya (r.a.)
The Expedition of Tabuk was an expedition in which the Muslims were exposed to great hardships and troubles. We understand from some verses and hadiths that they had big financial difficulties. Hz. Uthman gave one thousand dinars for the equipment of the army. This pleased the Messenger of Allah (pbuh) very much and prayed for him as follows: “O Lord! I am pleased with him; You be pleased with him too.”  Some Muslims wanted to take part in the expedition very much but they could not take part because there were not enough clothes, mounts and weapons. They shed tears because of it. Those Companions are mentioned as follows in the Quran:
“Nor (is there blame) on those who came to thee to be provided with mounts, and when thou saidst, ‘I can find no mounts for you,’ they turned back, their eyes streaming with tears of grief that they had no resources wherewith to provide the expenses.” 
Ibn Ishaq narrates the following while explaining that verse:
“Some Muslims came to the Messenger of Allah. They were poor. They wanted mounts from the Messenger of Allah. He did not have any mounts to give them. They return by shedding tears because they did not have anything to spend in the way of Allah.” 
Ibn Ishaq writes that six of them were from Ansar and that Irbad bin Sariya, one of the oldest Companions of Suffa School, was among them.
This heroic Companion, who was educated about the truth by the Messenger of Allah in Suffa School, was praised by the Quran along with the other Companions who could not take part in the Expedition of Tabuk. They could not take part in the expedition but we understand from the statements of the Prophet that they received as many thawabs as those who took part in it. The Messenger of Allah states the following about them:
“In Madinah, there are people who were with you as you traveled and crossed valleys.”
Thereupon, the Companions said, “O Messenger of Allah! Even though they were in Madinah?” The Messenger of Allah said,
“Yes, even though they were in Madinah. For, they were kept behind by legitimate excuses.” 
Irbad bin Sariya was one of the oldest Companions of the Messenger of Allah. God Almighty granted him a long life. He often prayed to Allah to join Him: “O Allah! I have become old; my bones have weakened. Take me into Your presence.” 
Irbad bin Sariya was a loyal student who always attended the talks of the Messenger of Allah. Irbad bin Sariya sometimes narrated his memories with the Messenger of Allah. He said one day after the morning prayer, the Prophet turned toward the Companions and gave them some emotional advice and that the Companions wept due to fear.
Irbad continued as follows:
One of the Companions said, “O Messenger of Allah! It is as if this was a farewell sermon. What do you advise us?” The Messenger of Allah (pbuh) said,
“I enjoin you to have fear of Allah and that you listen and obey even if an Abyssinian slave is made a ruler over you. He among you who lives long enough will see many differences. So, for you is to observe my Sunnah and the Sunnah of the rightly-guided caliphs, holding on to it with your molar teeth. Beware of newly-introduced matters (bid’ahs), for every new matter is an innovation (bid’ah) and every innovation is a misguidance.” 
This great Companion, who died in 75 H, spent most of his life in Damascus and the last part of his life in Homs. Despite his old age, he regarded it his purpose to spread the truths and beauties of the religion until he died.
May Allah be pleased with him!
Sirah, 4: 161.
Ibn Majah, Jihad: 6.
Hilya, 2: 14.
Abu Dawud, Sunnah: 6; Usdul-Ghaba, 3: 399.