Robert Squires claims that what Mohammed did was no different than what Abraham and the Israelites allowed. His conclusion was "if it was good enough for Abraham it is good enough for me". Well, the fact is, it wasn’t good enough for Abraham and the Israelites.
The Baker Ency. of the Bible says about Jewish marriage customs in volume 2, page 1407, under "Marriage":
"Subsequently, minimum ages (for marriage) of 13 for boys and 12 for girls were set."
And Jim West, ThD, writes online, in "Ancient Israelite Marriage Customs":
"The wife was to be taken from within the larger family circle (usually at the "outset of puberty" or around the age of 13) in order to maintain the purity of the family line".
Even in the Mishnah, the age of maturity for a female is 12.5 years:
"she won her case in court before she matured [at the age of twelve years and six months], lo, they belong to the father." Mishnah Ketubot, 4:1. Jewish culture allowed young girls to be married at an early age but not as young as 9.