In the beginning of Exodus 30:12-13, God commands Moses not conduct a head count of the Israelites before they go into battle against future adversaries:
“When you take a census of the Israelites who are to be registered, each one, as he is enrolled, shall give the LORD a forfeit for his life, so that no plague may come upon them for being registered. Everyone who enters the registered group must pay a half-shekel, according to the standard of the sanctuary shekel, twenty gerahs to the shekel. This payment of a half-shekel is a contribution to the LORD . . . ”
Interesting passage, isn’t it? Why not conduct an actual head count? The biblical writer may also indirectly be alluding to a census that King David carried out toward the end of his reign, which produced disastrous consequences (2 Sam 24ff.).
The answer to this question has a lot to do with the ancient’s fascination with numbers and the process of counting. Here’s the background information: Numbers play a very important part in our everyday lives. Life constantly demands that we measure and count. Numbers have always played a role in all civilizations from mathematics to astrology. Numbers also play an important symbolic role in much of the Bible, e.g., one, two, three, four, five, seven, twelve, forty, fifty, seventy, hundred and thousand. This is not the place to examine the significance of each of these numbers, but they often have symbolic and rhetorical significance.
The famous anthropologist Sr. James Frazer notes that certain African tribes were afraid to count children for fear that the evil spirits might hear. They also believed that cattle should not be counted because it might impede the increase of the herd.  In Denmark, there was a tradition not to count hatched chickens lest some be lost. In German cultures it is believed that the more you count your money, the more likely you will decrease it. 
Gamblers know this truth all too well; just listen to the old Kenny Rogers song, “The Gambler”:
You got to know when to hold ’em, know when to fold ’em,
Know when to walk away and know when to run.
You never count your money when you’re sittin’ at the table.
There’ll be time enough for countin’ when the dealin’s done.
In a minyan, pious Jews are accustomed to count Not One, Not Two, Not, Three, and so on. Why would any normal people, want to count in such a bizarre sort of way? (On a light note, I personally never thought this system of counting ever made a great deal of algebraic sense.)
Perhaps the biblical writers wanted to tell us is that it is one thing to count objects, it’s another thing to count people. A human being must never be quantified as a number. The Torah tells us that when Moses took a census of the Israelites, he had all the males of military age donate a shekel, and by counting the Shekels, he knew the exact amount of the Israelites he had.
Therefore, Jewish tradition teaches that when we count, we must not use numbers when counting people. Why? Because a human being is not a number.
A plane crashes, 350 people die. Most people just forget about the terrible news without thinking much about it. In the world, 40,000 children die daily from starvation or disease. Here too, for most of us, this is only a number. Whenever a catastrophe like an earthquake or a tsunami results in the loss of 100,000 people or more, how can we possibly understand or grasp what this number even means? For us, in the comfort of our living rooms in the affluent sections of Beverly Hills or Manhattan, the reality of these tragedies really do not touch our soul until we can literally see what is going on with our own eyes. Being at the disaster is bound to make a much more permanent impression on our psyches.
The number may seem insignificant until you actually see a starving child, or picture of a earthquake victims in Haiti or Chili, whose grief will say more than a 1000 words.
Numbers sometimes depersonalize. A human being is not a statistic. In times of war, killing often becomes like playing some computerized video game. For Jews, this is nothing new. Numbers are often obscene. Who among us will ever be able to fathom the death of 6 million Jews? When the Nazis herded the Jews to the concentration camps, they stripped them not only of their clothes, names, but also branded them with a number, thus attempting to strip the inmate of his or her last trace of human personhood.
It is only when we put a human face upon the victims, only then does the reality of murder and death becomes real.
Numbers camouflage the true value of a human being in other ways that are ordinary.
Over 400,000 a year die from smoking cigarette related illnesses. The number may not mean much to you unless one of the people happens to be your mother or father, a sibling, a close friend, or a beloved spouse. Close to 8,000 people between 15 and 24 were killed in alcohol-related traffic accidents in 2008, and an additional 320,000 were injured. (Source: U.S. Dept of Health and Human Services) Thousands of young people commit suicide every year, yet the number may not mean much to you unless you know a young person who has committed suicide.
Once we can attach a face to a number, suddenly we are affected by the loss of the individual.
I remember many years ago, I was attending a high school class. The young man sitting next to me accidentally electrocuted himself on the following day. I will never forget the sense of loss I noticed, when the chair sitting next to me after this young person’s burial–was empty. Somehow, when you personally know the victim, the loss becomes that much more magnified.
 Frazer writes: “For example, among the Bakongo, of the Lower Congo, “It is considered extremely unlucky for a woman to count her children one, two, three, and so on, for the evil spirits will hear and take some of them away by death. The people themselves do not like to be counted; for they fear that counting will draw to them the attention of the evil spirits, and as a result of the counting some of them will soon die. In 1908 the Congo State officials, desiring to number the people for the purpose of levying a tax, sent an officer with soldiers to count them. The natives would have resisted the officer, but he had too many soldiers with him; and it is not improbable that fights have taken place between whites and blacks in other parts of Africa, not that they resisted the taxation, but because they objected to be counted for fear the spirits would hear and kill them.”1 Similarly among the Boloki or Bangala of the Upper Congo, “the native has a very strong superstition and prejudice against counting his children, for he believes that if he does so, or if he states the proper number, the evil spirits will hear it and some of his children will die; hence when you ask him such a simple question as, ‘How many children have you?’ you stir up his superstitious fears, and he will answer: ‘I don’t know.’ If you press him, he will tell you sixty, or one hundred children, or any other number that jumps to his tongue; and even then he is thinking of those who, from the native view of kinship, are regarded as his children, and desiring to deceive, not you, but those ubiquitous and prowling evil spirits, he states a large number that leaves a wide margin.”James Frazer, Folk-Lore in the Old Testament Studies in Comparative Religion Legend and Law Vol. 2 (New York: Macmillan, 1917), 556.
 Ibid., 559-560.