שמות פרק לח , כב וּבְצַלְאֵׁל בֶן-אוּרִ י בֶן-חוּר לְמַטֵּׁה יְהוּדָה עָשָׂה אֵׁת כָל-אֲשֶׁר-צִוָּה ה' אֶת -משֶׁה :
ירושלמי מסכת ברכות דף לג/ב פרק ד הלכה ג גמרא
בכל יום אדם מתפלל שמונה עשרה רבי שמואל בר נחמני בשם ר' יוחנן כנגד י"ח ציוויין שכתוב בפרשת משכן שני אמר רבי חייא בר בלבד מן ואתו אהליאב בן אחיסמך למטה דן עד סופיה דסיפרא
This refers to the 18 times that it is written in Parshas Pekudei "אשר צוה" with the exception of the above verse, since this verse only mentions Betzalel and not Ohaliav.
Why does the Gemara refer to this as the second Mishkan? One answer is that the construction of the Mishkan is mentioned in two places. Thus, Parshas Terumah would be considered the first Mishkan, and Parsha Pekudei would be the second place that mentions the Mishkan.
Another understanding could be a connection with the opening verse of the Parsha that states the word Mishkan twice. Thus, the concept of Mishkan exists twice, once while standing and a second time when it is not standing (not available as in pawned). This is similar to the words of Bilaam “How good are your tents Yaacov, משכנותיך Yisrael”, which one Medrash interprets as how good are your tents which they are built, and even your משכון (meaning an item of collateral) when they are destroyed (not available). Thus, after the Mishkan was destroyed and korbanos were no longer offered, the Jews still have the ability to seek forgiveness through prayers. And as an allusion to the connection between the Mishkan and prayers, each contained a concept of 18.
שמות פרק מ , ז וְנָתַתָ אֶת-הַכִיֹּר בֵׁין-אֹּהֶל מוֹעֵׁד וּבֵׁין הַמִזְבֵׁחַ וְנָתַתָ שָׁם מָיִם :
This verse is an allusion to the halacha that immediately after washing for bread, one should make no interruption and proceed to making the blessing on the bread. The Kiyor is an allusion to the washing basin in one’s house. The Ohel Moed is the source of blessings due to the Divine Presence. And the table of the righteous is like the Altar. Thus, one places the Kiyor (washing one’s hands) in between the Ohel Moed (the blessing on ritual washing of one’s hands) and the Mizbeach (the table were the food is eaten) without any separations (making the blessing on the bread immediately).
100 Sockets
שמות לח,כז : וְאֵת אַדְנֵי הַפָּרֹכֶת מְאַת אֲדָּנִים
Correspondingly, says the Ba'al haTurim, they later instituted the recital of a hundred Berachos per day. This is most appropriate, since the sockets are called 'Adonim' (from the word 'Adon' - master), and what is the purpose of a Beracha if not to acknowledge that G-d is our master, in whichever facets that particular Beracha covers.
Other allusions from 100 include:
מְ יֻסָדִים עַל-אַדְנֵׁי -פָז (שר השרים ה,טו) the word על has a Gematria of 100 as if to read “set into 100 sockets (and plated with) finest gold.
100 amos high walls of the Bais haMikdash
