One of the Rabbinic concepts with which I have been deeply taken appears twice in Masechet Shabbat:

Shabbat 10a

Every judge who judges with complete fairness even for a single hour, the Writ gives him credit as though he had become a Partner to the Holy One, Blessed Be He, in the Creation.  (For) here it is written, (Shemot 18:13) “And the people stood about Moshe from the morning into the evening”; whilst elsewhere it is written, (Beraishit 1:5) “And there was morning, and there was evening, one day.”

Ibid. 119b

R. Hamnuna said: He who prays on the eve of Shabbat and recites (Beraishit 2:1) “And (the heaven and the earth) were finished,” the Writ treats of him as though he had become a Partner with the Holy One, Blessed Be He, in the Creation, for it is said, (Ibid.) “VaYechulu (and they were finished);” read not “VaYechulu” but “VaYechalu (and they finished).”

Although each of these interpretations is justified in the Talmud by an application of a hermeneutic principle, i.e., the former by the rule of “Gezeira Shava” whereby the utilization of a similar word or phrase in two different biblical verses is understood to represent a link between them; the latter a “Ktiv/Kri” where because the text is written without vowels in the Tora, it can be read in a manner other than how the tradition has established it to be read), the common denominator is the presumption that a partnership be established between God and man in the interests of perfecting the world— a form of Tikkun Olam.

While the two cases in the Talmud are specific and thereby relatively limited in the sense  that in the first instance, only some people even qualify as judges, thereby precluding all those who either do not have the ability or who are inherently disqualified from occupying such a role within society, and regarding the second, reciting a Tora passage within the context of the weekly Shabbat liturgy, while available to a far wider group of people, nevertheless is extremely metaphysical in its effects, I have always felt that conceptually, “partnering with God” in all sorts of capacities represents the religious ideal for human beings.

Such an infinite broadening of the concept appears in a symbolic approach offered by Meshech Chachma writing in his commentary on BaMidbar 15:40, with respect to the Mitzva of Tzitzit:

…In every matter having to do with any aspect of the Creation (which the commentator likens to a “garment with unfinished threads hanging from its corners) when we do a Mitzva, it connects you to the Lord, may He Be Blessed…and in this way the Creation will realize its true perfection in accordance with the Intention of the Holy One, Blessed Be He. And you, man, if you “weave” (in a manner comparable to completing the Tztitziyot on the corners of a four-cornered garment) the Creation, you will be a partner with the Holy One, Blessed Be He, in the Creation…

R. Walter Wurzburger, in the chapter entitled “The Search for Meaning and Purpose” in God is Proof Enough, suggests an interpretation of a biblical text that, at least to my mind, expands this theme even further:

As a rule, the creation of the various natural phenomena is introduced by the phrase, “Let there be…” But in describing the Creation of man, the Book of Genesis refrains from employing this expression and replaces it with “Let us make.” The emphasis upon making in the creation of human beings indicates, that unlike other creatures, man is not a finished product but is forever in the making. Thus, in the biblical view, humans have no fixed, predetermined nature. We are what we make of ourselves. As the existentialist philosopher, Karl Jaspers, put it, “To be a man is to become a man.” …

Despite the fact that R. Wurzburger does not say so in as many words, it seems to me that when God states, “Let us make” with relation to man, it could be understood that God “Partners” with man to the extent that man decides to sanctify himself and live according to Tora and Mitzvot, so that man becomes what he potentially could in accordance with his innate “Tzelem Elokim.” Such an understanding also seems to me the implicit meaning of what R. Wurzburger writes about Teshuva:

Although Teshuva is frequently mistranslated as repentance, its real meaning is returning (to what we would have become, had we not deviated from the proper path.) Essentially, Teshuva amounts to self-creation. As long as a human being is alive, s/he has the potential to acquire a new identity.

Consequently, partnering with God not only allows man to be a “player” in the perfection of Creation, but also in the perfection of himself, noble goals for the truly religious lifestyle.