Excellent question. We began celebrating the holiday of Passover on the first anniversary of our freedom from Egypt. Actually, in practice we celebrated it even during the actual Exodus, as we were commanded by G‑d to eat the Passover lamb on the night prior to the Exodus.
Your question, however, brings out a very interesting point. During the forty years we traveled through the desert, although the holiday was presumably observed, the only time we brought the Paschal Offering was on the Exodus' first anniversary. The next time the Jewish people brought this offering was 39 years later, when they entered Israel.
"Why?" you ask. Why did the Jewish people not offer the Paschal Lamb for 39 consecutive years? This seems rather unbecoming of a young nation that had itself experienced the great miracles of the Exodus. The biblical commentator Rashi comments on this point, quoting a Midrash which says that this was not one our proudest memories.
Interestingly, we weren't asked to bring the Paschal Offering throughout those desert years. G‑d commanded us to offer a lamb as a Passover offering on the first anniversary and did not ask of us to do this again until 39 years later. And since we weren't commanded to do so, it would have been forbidden to offer an offering in the Tabernacle that was not requested by G‑d.
Then why the embarrassment? What is the big deal that we did not bring a Passover offering for 39 years? We weren't told to; had G‑d commanded us to do so we would have certainly fulfilled His request!
Rabbi Menachem Schneerson, the Lubavitcher Rebbe, offers the following explanation:
Sometimes a person needs to take the initiative. He needs to exhibit his interest in the matter and act upon it without waiting to be asked. Many times a parent waits to see their child show interest and independent action. That brings the parent the greatest pride and joy.
This should have been our approach in the desert. Yes, G‑d did not ask us to offer a Passover sacrifice for those 39 years. However, we were a young nation in the process of growing and maturing. More importantly, we were a young nation which soon after receiving the Torah sinned against our G‑d (the story of the Golden Calf). We needed to show G‑d, and perhaps more importantly, to show ourselves, that we were interested in G‑d's commandments; we were excited to do them. Had we only expressed our sincere wish to offer a Paschal Offering, G‑d would have certainly fulfilled our request and allowed us to do so during the 40 years we traveled in the desert.
In fact, that is exactly what happened during the first anniversary celebration. There was a group of people who were ritually impure and could not partake in the celebration; they were not allowed to bring a Passover offering. They therefore complained to Moses: "Why should we lose out?" G‑d responded like the proud parent and gave them a second opportunity – the "Second Passover"; a second chance to bring the Passover offering. To this day the Jewish nation celebrates an additional holiday because of the request of this group of people.
From this we can derive an eternal lesson; one that is applicable to all times and all places, specifically our times. G‑d wants to hear from us. He wants to hear our prayers and our requests. And He we will deliver.
We need to complain to G‑d: "Why should we lose out?" Why is our generation still awaiting the time He has promised us; the time when all sicknesses will be banished, when hunger will disappear, when war and hatred will forever be removed from our world; the time of our redemption through our righteous Moshiach? Why are there so many hundreds of mitzvot which we are denied the opportunity of fulfilling due to our exiled state and the lack of a Holy Temple?
And He will deliver.
All the best,
Rabbi Shmuel Kogan,