The Torah is the wisdom of God. This means, among other things, that its spiritual root is very high and descends to us just as it is in the higher worlds. Our sages explain that, technically speaking, the source of the Torah is at the level called Chokhmah—Wisdom.
One of the characteristics of this level (which is also found in the soul) is that it contains within itself the central point of an idea, within which, in a compressed and mixed form, are all the details of that idea. Like the father's seed, which contains within it all the qualities of the future living being but in a hidden and compressed form, the mother is responsible for developing and decompressing that initial drop, making it into a human being.
Consequently, at the level of Chokhmah, time does not exist. Just as space occupies no place, since a single point contains within it countless details fused together, in the same way, time—that is, the moment in which each of those details would occur—does not exist, and all events to occur are fused into an eternal present.
This explains why certain events in the Torah are not in chronological order. While every letter, every word, every phrase necessarily occupies space and time and must be ordered correctly to make sense, in its spiritual source, the Torah is not limited by space or time, and all its parashot—sections—occur simultaneously.
According to some commentators, this week's section, Terumah, is not chronologically ordered in the Torah, so it was transmitted at one time and introduced into the text at another.
According to the order of events as they appear in the Torah, this section comes after the Giving of the Torah (in parashat Yitro). After parashat Mishpatim, which deals with many rational laws, comes our section, Terumah.
However, there are those who say that this section was actually transmitted after the sin of the Golden Calf, that is, after parashat Ki Tisa (being between our parashah and Ki Tisa, the parashah Tetzaveh).
What is the difference if Terumah comes before or after the Golden Calf? The sin of the Golden Calf consisted, in short, of the Jewish people committing idolatry and turning away from God. Before this, the Jewish people had received the Torah at Mount Sinai, rising to the level of Tzaddikim—the righteous. At the time of the sin, the Jewish people lost this spiritual status and became Reshaim—the wicked. After repenting (after Yom Kippur—the Day of Atonement) the Jewish people attained a new status: Baalei Teshuvah—Masters of Repentance—a state in which the previous sin was forgiven or even erased.
It appears that if Parashat Terumah was transmitted before the sin, it was told to a group of Tzaddikim, whereas if it was told after the sin (in which case it would be out of order in the Torah), it was told to Baalei Teshuvah.
The main topic of this section is the construction of the Mishkan—the Sanctuary, where the Divine presence on Earth was revealed. Based on this, it is not the same to say that God asks a group of Tzaddikim to reveal Him on Earth (build a Mishkan) as it is to say that God asks the same of a group of Baalei Teshuvah.
The teaching of this opinion, which Parashat Terumah is not written in order, is that everyone, regardless of our past, can (and therefore should) take on the task of building God's Mishkan, His Sanctuary—that is, making this world a dwelling place for the Divine Presence. No one can say that it is not their job or that it is beyond their reach. Each and every one of us, according to our knowledge and abilities, can and should make the greatest effort to make the world a better place.