Circumcision is not cutting off half of the penis. It is only the foreskin. This was a requirement that God placed upon the people of Israel when he set them aside as his chosen people. You will find this article from the book "Insight On The Scriptures" enlightening. There are many references to scriptures in the Bible. You would do well to get a Bible and look these scriptures up.
The removal of the prepuce, or foreskin, from the male penis. The Hebrew verb mul (circumcise) is used in a literal and a figurative sense. The Greek noun pe·ri·to·me′ (circumcision) literally means “a cutting around.” (Joh 7:22) “Uncircumcision” is rendered from the Greek term a·kro·by·sti′a, which was used in the Greek Septuagint to translate the Hebrew word for “foreskin.”—Ro 2:25; Ge 17:11, LXX.
Jehovah God made circumcision mandatory for Abraham in 1919 B.C.E., a year before Isaac’s birth. God said: “This is my covenant that you men will keep . . . Every male of yours must get circumcised.” Every male in Abraham’s household of both his descendants and dependents was included, and so Abraham, his 13-year-old son Ishmael, and all his slaves took upon themselves this “sign of the covenant.” New slaves brought in also had to be circumcised. From then on, any male of the household, slave or free, was to be circumcised the eighth day after birth. Disregard for this divine requirement was punishable by death.—Ge 17:1, 9-14, 23-27.
Circumcision was practiced in Egypt, as is illustrated in wall paintings and observed in mummies, but it is uncertain when it was first introduced in that country and to what extent it was performed. Some say that Joseph as food administrator introduced it to Egypt. Others cite Herodotus as authority for their claim that Abraham simply borrowed the custom from the Egyptians. Answering these latter claims, W. M. Thomson says: “As to the testimony of Herodotus, who came into Egypt fifteen centuries after, and, with great learning and research, often writes a good deal of nonsense, I refuse utterly to put it in the same category with that of Moses. The great founder of the Jewish commonwealth—the greatest lawgiver on record—born and bred in Egypt, states the facts in relation to the introduction of circumcision among his people. A mere traveller and historian—a foreigner and a Greek—comes along very much later, and makes statements which are partly true, partly erroneous, as Josephus shows in his answer to Apion; and then sceptical authors, more than twenty centuries later than Herodotus, bring up his imperfect statements, and, twisting and expanding them, attempt to prove that Abraham did not receive circumcision from God (as Moses plainly says he did), but from the Egyptians! Not with such weapons can the veracity of Moses be successfully assailed.”—The Land and the Book, revised by J. Grande, 1910, p. 593.
Not only did the Egyptians practice circumcision but the Moabites, the Ammonites, and the Edomites also did. (Jer 9:25, 26) Later, the Samaritans that adhered to the requirements set out in the Pentateuch were also circumcised. On the other hand, the Assyrians, the Babylonians, the Greeks, and notably the Philistines did not practice circumcision. The latter in particular, rather than the Canaanites in general, are derogatorily spoken of as “the uncircumcised,” and it was from fighting with them that trophies of foreskins were brought.—Jg 14:3; 15:18; 1Sa 14:6; 17:26; 18:25-27; 2Sa 1:20; 1Ch 10:4.
Abraham’s descendants through Isaac and Jacob faithfully kept the covenant of circumcision. “Abraham proceeded to circumcise Isaac his son when eight days old, just as God had commanded him.” (Ge 21:4; Ac 7:8; Ro 4:9-12) The great-grandsons of Abraham told Shechem and his fellow townsmen: “We cannot possibly . . . give our sister [Dinah] to a man who has a foreskin . . . Only on this condition can we give consent to you, that you become like us, by every male of yours getting circumcised.” (Ge 34:13-24) Apparently because Moses neglected to circumcise his son, he incurred God’s wrath until his wife Zipporah did it for him.—Ex 4:24-26; see ZIPPORAH.
Circumcision Under the Law. Circumcision was made a mandatory requirement of the Mosaic Law. “On the eighth day [after the birth of a male] the flesh of his foreskin will be circumcised.” (Le 12:2, 3) So important was it that, if the eighth day fell on the highly regarded Sabbath, circumcision was to be performed anyway. (Joh 7:22, 23) Examples of parents under this Law who faithfully had their children circumcised on the eighth day include the parents of John the Baptizer, Jesus, and Paul. (Lu 1:59; 2:21; Php 3:4, 5) The Law also required aliens to be circumcised before they were allowed to eat the passover.—Ex 12:43-48.
Why did the Law specify that circumcision be done on the eighth day?
Jehovah did not explain, nor was it necessary that he do so. His ways are always right; his
Insight On The Scriptures