Parshas Terumah features the command to construct the Mishkan and its kelim (vessels). To be precise, in Parshas Terumah, Hashem first commands the construction of the most holy kelim – the Aron (Ark), Shulchan (Table), and Menorah – followed by commands to construct and erect the various sections of the Mishkan, formed by boards, curtains, sockets, and so forth.
 
There is one very important keli which is omitted from the initial command to construct the kelim: the Mizbeach (Altar). Unlike the rest of the kelim, whose command to be built appears in perek (chapter) 25 of Sefer Shemos, the Mizbeach is set apart and commanded to be built in perek 27, after the details of the Mishkan’s sections and their construction appear. Why is this? Why is the Mizbeach not featured along with the other kelim?
 
In fact, the Mizbach Ha-Zahav, the small Golden Altar, is likewise presented in a quite unusual context. The command to construct the Mizbach Ha-Zahav appears at the very end of Parshas Tetzaveh, following the rules of Kohanim and their vestments. Why is the Mizbach Ha-Zahav, akin to the (larger, bronze) Mizbeach (also referred to as the Mizbach Ha-Nechoshes), presented far away from the other kelim? Should not both the Mizbach Ha-Nechoshes and the Mizbach Ha-Zahav be featured along with the rest of the K'lei Ha-Mishkan (Vessels of the Mishkan)?  
 
On a simple level, the answer to why both Altars respectively appear at the end of Parshiyos Terumah and Tetzaveh, rather than at the beginning of Parshas Terumah along with the other most sacred kelim, is related to the function of the Altars. Whereas the Aron, Shulchan and Menorah are of inherent import on their own – their very presence conveys essential messages and fulfills an important role in the Mishkan, irrespective of active use – the Mizbeach is a purely functional article, whose import is limited to its use. Merely having a Mizbeach in place is not of value; rather, the value of a Mizbeach is its active sacrificial use. On the other hand, the Aron contains the Luchos (Tablets) and symbolizes Torah; the Shulchan represents Hashem’s provision, as exemplified by the Lechem Ha-Panim (Showbread) which the Shulchan holds; the Menorah is a sign of Hashem’s Presence among B’nei Yisroel (as Chazal state, the Menorah's Western Lamp signifies that the Shechinah resides among Yisroel). The very existence of these three kelim and their stationing in the Mishkan are of primary significance, for these kelim are fundamentally of an existential nature.
 
This is to be contrasted with the Altars, whose presence itself is not their main significance; rather, their active use is their main significance. For this reason, the Torah sets the Mizbach Ha-Nechoshes apart and features it near the end of Parshas Terumah, indicating that the Mizbeach’s main import is not in terms of it being part of the existential Mishkan structure, and the Mizbach Ha-Zahav likewise appears at the end of Parshas Tetzaveh (which addresses the Kohanim, as the Mizbach Ha-Zahav only handles Ketores and Yom Kippur offerings, which are related to Kohanim and are not brought on behalf of (non-Kohen) individuals). The Altars are primarily important in terms of their utility, as opposed to the other kelim, whose very presence in the Mishkan is of fundamental existential significance, unrelated to active use.   

On a deeper level, the message conveyed by the Torah's presentation of the Altars is that mitzvos are meaningful only when they are performed. There is no value to normative mitzvah objects as mere showcase pieces. A home which boasts an exquisite sterling Havdalah set, esrog box, Kiddush cup, and so forth - or a bookcase which is stocked with a spectacular array of beautifully-bound sefarim (holy books) - is sorely lacking if these objects serve only as furnishings and nothing more. Torah and mitzvos are meant to be learned and lived, and this is the message of the Mizbeach, which is meaningless as a furnishing and is defined only in terms of its active use to serve Hashem.

A very elderly teacher of mine once told our class in yeshiva, "I love torn (sacred) books." This teacher proceeded to explain how torn sefarim indicate that their owner learned much from them, and the teacher related to us how disappointed he would become when he would see old sefarim in mint condition, indicative that their owner has obviously not learned from them often. The teacher then proudly showed us his own small sets of Gemara and Rambam, which his grandmother gave him as a bar mitzvah gift some 70 or more years prior; these sifrei kodesh (holy books) were almost in tatters, testifying to their great, holy and scholarly owner, who personified the lesson of the Mizbeach by actively and most diligently learning from the sefarim on a continual basis.

May we too follow in his stead.