There are a variety of different answers given, ranging from compassion to love. At varying times, God orders a census. In this case, the surface reading would seem to indicate that the Israelites are about to leave Mt Sinai, so this count is purely an administrative task, to help organise the march.
However, reading a little deeper reveals a fascinatingly different interpretation. The second verse of the book reads:
“Take a census of the whole Israelite community” – שְׂאוּ אֶת רֹאשׁ כָּל עֲדַת בְּנֵי יִשְׂרָאֵל
S’u et rosh–literally translated means, “Lift up the head”. According to Ramban (not to be confused with Rambam), the word s’u is only used when the intention is to indicate greatness (that is, holding high one’s head). The point here is not simply to have the number of every male of military age. We are not interested in that number. We are not concerned with counting everyone, but rather, in making everyone count. The meaning is not in the numerical value, but in what those people represent.
My Rabbinate is not defined by those numbers of events that I had the privilege of participating in, but rather in the context and meaning that I was able to bring to those events, by the joy and simcha, comfort and meaning, inspiration and reflection that was created then and there in those moments. The Israelites are not defined by the sheer number of their mass, but by the meaning each and every one of them are able to create, by being an active part of their community. By counting each individual, God is helping us to realise our own self-worth.
As we come to this weekend where we on the precipice of renewing our relationship with God and our covenant at Shavuot, let us remember the special place we each have, not just in the number of our accomplishments, but in the deeper meaning that was created by us being a part of it.