it was a habit done by the gentlefolk of makkah to entrust their children to the women living in the desert to breast-feed them, because the desert was the best place for the growth of the children’s body, and it was the farthest from diseases of the urbanism, which attack their bodies frequently.
in addition to that is to make those children perfect their arabic language, and get used to talk classical arabic since an early age.
the amount of attention and care given to children differs from a tribe to another, so the gentle folks of makkah were much concerned that their children should be with the most caring tripe. the most reputed tripe in that issue was the tripe of bany sa’ad.
bany sa’ad’s reputation was beyond that; it was not only in taking care of children in a perfect way, but also because of their spoken arabic was a pure one, and they had good, respectable morals. therefore, muhammad’s grandfather abdel muttaleb was very much concerned to give his grandson to the tribe of bany sa’ad.
when halima al sa’dia ( the woman who breast-feeded muhammad pbuh ) came to take him and felt that his family is much concerned to make their child brought up in her tribe, she desired a high donation and so was paid by abdel muttaleb what she desired.
the prophet himself (pbuh) was proud of his growing up in bany sa’ad, and used to say: “i am the most arabian one of you; i am from quraish and was brought up in bany sa’ad bin bakr”
some historians mention that muhammad was presented to all wet nurses who came to makkah and they refused to take him for being an orphan and poor, they desired the rich people’s children, and that halima took him just because she did not find another child. in the contrary, that was not true. muhammad was not poor he was living in his grandfather’s house abdel muttaleb; the master of quraish that all people like to get some of his wealth. sources mentioned that abraha’s army in his assault on ka’ba acquired two hundreds of camels of abdel muttaleb.
abdel muttaleb also ransomed his son abdullah with one hundred camels, and slayed a heap of camels in his marriage, so that all people did eat from it.
al-ya’kouby mentioned that when abd el muttaleb died he was wrapped up in two costumes (yemen’s costumes) that worth one thousand molecules of gold.
you believe after all this that no one of bani sa’ad’s women wanted to have muhammad to grow up in her house.
muuhammad (pbuh) spent four or five years with the family of (halima bent aby thu’aib al sa’dia) and her husband (al haarith ben abdel ozza). then something happened made her accelerate returning him to his mother in makkah; when her young son told her that two men took muhammad and split his chest and extracted a black leech from it and washed his heart and returned it to its place. historians differed in the truth of the split of the heart if it is perceptible or abstract. however, it may refer to inaccessibility that allah gave muhammad – peace be upon him- that reinforced him against natural humanity offences and earthly life temptations.
his foster brothers are –peace be upon him:
abullah ben al haarith, anisa bent al haarith, huthafa bent al haarith (known as ash-shaima’: her nickname) that was very close to the prophet - peace be upon him.
the prophet’s childhood at bany sa’ad’s had its effect on his carnality shape and on his mental alternation in prospective. his preparation for mental meditation was shaped there since his early age.
etiene denie, the french orientalist, says in his book "muhammad, allah's messenger": "such body and behavioral health which he (pbuh) owed to the desert, had helped him a lot in enduring the hardships he had to face. muhammad (pbuh) loved to remember such period, he used to say "among the invaluable blessings that allah (the almighty) had bestowed on me is that i was born in quraish, the noblest of the tribes. that i was raised up in the desert of bani sa’ad, the healthiest place in hijaz". such images that were among the first elements that affected his feelings, kept engraved in his soul; those of him shepherding the cattle and watching over them in their grazing areas.
such readiness for meditation and loneliness was not compatible with the riotous manners of his fellow friends, that's why he used to seclude himself from them and stay alone where he can find calmness and serenity.