Sforno on Numbers 9:1

בחדש הראשון. אחר שפקד אנשי הצבא וסידר הדגלים ונושאי המשכן להכניסם לארץ וטהר מחניהם מן הטמאים כאמרו והיה מחניך קדוש (דברים כג, טו) ומן הממזרים בענין הסוטה למען תהיה השכינה ביניהם במחנה צבאותם ספר הכתוב ארבעה מעשים טובים שעשו ישראל שבהם זכו ליכנס לארץ מיד בלתי מלחמה לולא המרגלים כמו שהעיד משה רבינו באמרו לחובב נוסעים אנחנו אל המקום. ראשונה סיפר חנוכת המזבח. שנית זריזותם בענין חינוך הלויים. שלישית זריזותם בקרבן הפסח. רביעית לכתם אחרי האל יתברך במדבר אף על פי שהיה העלות הענן בזמנים בלתי נודעים פעמים ארוכים ופעמים קצרים באופן שהיה ראוי שתקשה עליהם מאד החניה והמסע. ולהודיע כל אלה ספר אותם כפי מדרגת היותם לרצון לפניו לא לפי הזמן שהיו בו ולכן ספר בכאן ענין חנוכת המזבח והלויים והפסח שהיו בחדש הראשון והיתה תחלת הספר בחדש השני והיה ענין חניתם ונסיעתם על פי ה' מיום צאתם ממצרים ועל כמו זה אמרו אין מוקדם ומאוחר בתורה וזה כאשר תכוין תכלית מה זולתי הזמן בסדר המסופר: בחודש הראשון, after he had taken a census of the males fit for service in the army according to their ages. Moses was to make all the preparations necessary to arrange for the orderly entrance of the Israelites into the land of Canaan.
This involved first and foremost that the inhabitants of the camps of the Israelites be ritually pure in conformity with the Torah’s imperative that the army of the Jewish people when assembled must be holy (Deuteronomy 23,15). Needless to say that it must not contain people who had not cleansed themselves of their ritual impurity. They also had to be certain that no members of the Israelite camp was the product of an illegal union between people whose incestuous relationship carried the karet penalty. The purpose of all this was that G’d’s Shechinah would rest on the troops, and that therefore victory would be assured and casualties minimized.
The Talmud in Sotah 11 and 31 relates that the Jewish people had 4 virtues to their credit on account of which they merited entering and conquering the land of Canaan already at that time if the sin of the spies had not intervened. We know that Moses was convinced that the conquest of the land of Canaan was at hand when he asked his father-in-law Yitro to remain with him and to partake in that event. (Numbers 10,29)
These merits were: 1) the altar had been successfully consecrated, the offerings of the Jewish people were being accepted by G’d. 2) the Levites had been consecrated. 3) The Jewish people had demonstrated eagerness when observing the anniversary of the Exodus by performing the required ceremonies in difficult circumstances. 4) They had followed their G’d to an inhospitable desert even though they had no idea if and when the cloud would lift and indicate that they were suddenly to break camp. Their entire situation was such that sometimes they would remain in the same spot for months or years, whereas other times they would break camp and re-establish camp after only 24 hours, all of which involved a tremendous upheaval when we consider that we speak about two and a half to three million souls.
In order to describe the various merits the Jewish people had in their favour at the time the Torah told us at this point about these events instead of relating them in chronological order, as we might have expected. Consecration of the altar occurred in the first month of the second year, so did the consecration of the Levites, and so did the celebration of the second Passover. Seeing that the beginning of the Book of Numbers speaks of events in the second month of that year, we could have questioned the Torah’s sequence. However, the Torah had a purpose in delaying the report about the last mentioned events in order to demonstrate that had it not been for the disastrous mission of the spies everything would have been in place for an immediate ascent to the Holy Land. The entire paragraph is another illustration of the principle known as אין מוקדם ומאוחר בתורה, that the Torah is not a record of events in chronological order. The Torah most certainly is very orderly, has been written after careful consideration, but G’d, the author, had decided that “order” does not necessarily mean “chronological sequence.”