Circumcision in the Bible
Circumcision was instated in Genesis 17 as a sign of the covenant that God made with Abraham, and of which Jesus is the final fulfillment. At that time circumcision was already practiced by surrounding peoples, but as a rite of passage from boyhood to manhood. Biblical circumcision is unique for being applied to eight days old infants. Some claim that the benefit or function of circumcision is hygienic, but the Bible never even remotely hints at that. But to say that in the Bible circumcision is solely religious may not be entirely true.
Circumcision is difficult to explain. It seems at odds with the prohibition of ritualistic laceration (Deuteronomy 14:1, Leviticus 19:28, see also 1 Kings 18:28 and Jeremiah 16:6) and also seems a bit over the top. Since covenantal Hebrews can be recognized from afar by specific dress, attitude and behavior; it is not immediately clear why also the foreskin needed to be removed. The laws against exposure made sure that a circumcised penis remained largely unseen, and it seems that circumcision was meant as a very private sign.
As early as Deuteronomy 10:16 circumcision is explained as a physical sign for a mental attitude: the circumcision of the heart (or ear—Jeremiah 6:10), denoting a willingness to listen to instruction and an openness for correction with as ultimate result a loving of the Lord with all the mind, heart and soul—see Deuteronomy 30:6, which ties into Matthew 22:36-40, the discussion of the Greatest Commandment. That physical circumcision was an outward sign of an inward attitude, even massively outshone by it, becomes clear in texts such as Joshua 5:2, where the Lord commands Joshua to circumcise the sons of Israel a second time. Obviously, this is physically impossible, but the Lord wouldn't command it if it couldn't be done, and the result is Gibeath-haaraloth; the Hill of Foreskins. In Jeremiah 9:25-26, the Lord states, "Behold, the days are coming that I will punish all who are circumcised and yet uncircumcised—[...]all those [...] who clip the hair on their temples; for all the nations are uncircumcised, and all the house of Israel are uncircumcised of heart."
When Paul debates circumcision with some Judeans (Acts 15:1) and the Galatians (2:3-14, 6:15) he is by no means making a bagatelle out of the laws of Moses, but expounds them to their most sublime extent.
These statements also show that the Hebrews saw the reproductive region as 'heart' of the body, which may indicate that circumcision was aimed at the male's most intimate self.
But perhaps it wasn't aimed at the man at all. Perhaps the circumcision of the husband was for the sake of the wife...! That would certainly match marvelously what we previously discovered about the function of long hair on a woman's head.
Circumcision and wives
Since circumcision for medical reasons is quite common in the civilized world, the side effects have been studied at length. Apparently, and much against intuition, the glans (=head) of an uncircumcised penis is equally sensitive as one of a circumcised one. However, with the removal of the foreskin, much sensory material (some quite specialized) is lost. That means that the sensitivity of the penis at large diminishes. In general, circumcised men take longer to ejaculate, and they also tend to be less penis-focused, which makes them in general more creative in bed.
And sure enough, many studies reveal an increase of alternatives, such as oral and manual sex, in couples of which the man is circumcised.
And Sarah laughed
Of course, the birth of Isaac is miraculous on all accounts but could it really be that the purpose of Abraham's circumcision was to give more pleasure to Sarah? Pleasure is certainly a major theme in the covenant cycle. Right after Abraham circumcises himself and all the males in his household, Sarah says, "After I have become old, shall I have pleasure, my lord [Abraham] being old also?" (Genesis 18:12).
Some fascinating scientific investigations have revealed that pleasure and fertility go hand in hand. In fact, the female orgasm greatly enhances the chance of conception. Or as Ian Kerner PhD states (in an article posted on eDiets, which was recently removed), "It's been shown that when women orgasm after their partner has ejaculated inside them, the "upsuck reflex" kicks into gear: vaginal contractions that pull the sperm up into the cervix where the little mites have a better chance of encountering an egg."
And the argument that the conception of Isaac was a major miracle simply because Abraham and Sarah were thoroughly geriatric is also not valid. When Sarah conceived of Isaac she was 90 and Abraham was 99 (Genesis 17:1, 17), but those ages should be viewed relative to lifespan, and human lifespan in those days, though declining, was still about twice the length of ours. Sarah lived to be 127 (Genesis 23:1) and Abraham was 175 when he died (25:7). At the conception of Isaac, Sarah probably just stopped being fertile. After she died, Abraham, who was then 136 years old, married Keturah and fathered another six sons (Genesis 25:1-4).
Paul explains that Sarah could conceive of Isaac (means, He Will Laugh) because she had faith (Hebrews 11:11). Perhaps her faith was induced simply because the Lord said that she would conceive. Perhaps it was strengthened because of the foretold destruction of Sodom and the other towns. But Abraham's new and improved sexual skills may certainly have helped.