Noble families of the Quraysh had a custom of sending their newborns away from Makkah to be nursed and raised by women of the desert. There were several reasons for this. The desert protected children from the diseases of crowded towns, hardened them for a difficult life, and kept them from being spoiled by relatives. Above all, certain desert tribes were famous for speaking the purest and most fluent Arabic, free of the borrowed words of the city. The most famous of these tribes was Banu Sa'd ibn Bakr, and it was they who fostered the Prophet ﷺ. Every year, the women of Banu Sa'd came to Makkah to take in infants of the Quraysh in return for payment. Halimah al-Sa'diyah and her husband were very poor. She had just had a baby son of her own, so she had milk to nurse another child. That year she came to Makkah hoping to find a newborn to nurse for two or three years. Every other woman in her group found a child to foster, but Halimah did not. The only child left was the orphan whose father had died. The other women had passed him over, because they expected little payment from a family with no father. With nobody else left, Halimah agreed to take him. At once, her household saw blessings. An old goat that had long stopped giving milk began to give milk again, and their old riding animal became the fastest of the whole group. Fostering usually lasted two years, but Halimah saw so many blessings that she wanted to keep him longer. The Prophet ﷺ's mother, Aminah bint Wahab, agreed, even though she could not pay as much as the other families were paying.
As a small child, the Prophet ﷺ was raised in the desert by his foster mother, Halimah al-Sa'diyah. When he was four years old, he was playing with the other children when the angel Jibril came to him. The other children ran away in fear, but he stood his ground. Jibril overpowered him and laid him on the ground. He opened his chest and took out his heart. He removed a black portion from it and threw it away, saying that this was shaytan's portion in him. He then washed the heart in a golden cup of Zamzam water, put it back and sealed the chest. Halimah's young son and her daughter Shayma ran to her screaming that their brother had been killed. Halimah rushed out and found him sitting with a pale face. He was frightened, but he was not screaming or crying. A line remained on his chest ﷺ where it had been opened, and it could still be seen late in his life. The incident worried Halimah, and she decided then and there to return him to his mother, Aminah.
At the Battle of Hunayn, the Muslims fought and defeated several tribes. Among them was Banu Sa'd ibn Bakr, the desert tribe that had fostered the Prophet ﷺ when he was a baby. After the battle, the prisoners of war were led to Ji'ranah. One of the women began to shout, asking how they dared treat her this way when she was the sister of their own companion. She was Shayma, the daughter of the Prophet ﷺ's wet-nurse, Halimah al-Sa'diyah, and so his foster sister. She had helped care for him as a baby, some 56 years earlier. The astonished companions told the Prophet ﷺ, and he asked them to bring her to him.
Halimah al-Sa'diyah and her husband had not been present at Hunayn, and only came to visit afterward. When the Prophet ﷺ saw her, he recognized her instantly, stood to greet her, and took off his own shawl to spread on the ground for her to sit on.
The Banu Sa'd ibn Bakr were the tribe of Halimah, who had cared for the Prophet ﷺ in the desert when he was an infant. They were a branch of the Hawazin, who had fought the Muslims at Hunayn. Unlike the Thaqif, who lived in the town of Ta'if, the Hawazin were Bedouins, and their manners were rough. In the ninth year of the Hijrah, shortly before the Thaqif came, the tribe sent one of its elders to Madinah to negotiate a peace treaty. He was not yet a Muslim. His name was Dimam ibn Tha'laba. He was a hairy, unkempt man who wore his hair in two ponytails, as Bedouins often did. He rode his camel right up to the door of the mosque, sat it down there, and walked in. "Where is the son of Abdul Muttalib?" he asked. He could not read or write, but he knew the Prophet ﷺ's famous grandfather, and for a man like him lineage mattered a great deal. The Prophet ﷺ said, "I am the son of Abdul Muttalib." Dimam asked whether he was Muhammad ﷺ, and he said that he was. Dimam said, "I will ask you, and I will be very tough with you, but don't get angry with me." The Prophet ﷺ said, "Go ahead." Dimam said, "Your envoy came to us, and he told us that Allah has sent you." The Prophet ﷺ said, "He has spoken the truth." Dimam then asked who created the heavens, who created the earth, who created the mountains, and who put everything in its place. Each time, the Prophet ﷺ answered, "Allah." Then Dimam asked him, by the One who had created all of these, to swear whether Allah had sent him to them. The Prophet ﷺ said, "I swear by Allah, I have been sent by Allah." Dimam went on in the same way. He said the envoy had told them they must pray five times a day, and asked, by the One who had sent him, whether Allah had commanded this. The Prophet ﷺ said, "Yes." Dimam asked the same about zakat, fasting and Hajj. The mention of Hajj fits the ninth year of the Hijrah. According to some narrations, Dimam is the man in a well-known hadith who asked whether he had to do anything more than these duties. The Prophet ﷺ told him, "No, unless you want to." The man then swore by the One who had sent the Prophet ﷺ with the truth that he would do exactly this, adding nothing and leaving nothing out. As he left, the Prophet ﷺ remarked to the Companions, "If he is true, then he shall enter Jannah." Dimam went home and preached to his people. Ibn Ishaq reports that he was so respected that the whole tribe accepted Islam on the day he returned. That same day he destroyed the idol they used to worship. It is said that no delegate was ever a greater blessing to his people than Dimam.