It is time to work for the Lord (et la'asot, he-feru Toratekha) is the first half of a verse in Psalms that has served as a dramatic slogan at several junctures in rabbinic Judaism.
Psalm 119:126 states: "It is time for the Lord to act, for your law has been broken" (New Oxford Annotated Bible ad loc.) This verse would seem to suggest that, when the wicked are breaking the commandments, God will deliver the steadfast.
However, in the readings of rabbinic midrash, an alternate meaning of the verse is given, due to an ambiguity in the Biblical Hebrew: instead of God acting in response to sin, humans should act on behalf of God. Thus, the verse may be understood as: "It is time to work for the Lord..."
As a result, even in the tannaitic period, the sage Hillel the Elder cited the verse to call fellow Jews to intensively study the Torah when it is neglected. (Ephraim Urbach interprets Hillel as calling for fuller observance of the Torah commandments in general, The Sages pp.341f.) Rabbi Nathan makes a related gesture, for Jewish efforts against heresy, at the end of Mishnah Berakhot. Nathan transposes the two halves of the verse thusly: "They have made void your law, it is time to work for the Lord." (See Urbach, 836n.93)
In the Talmudic period, the verse is thus called upon to justify the radical shift in rabbinic belief after the destruction of the Temple. Due to the conditions of exilic Jewry, the rabbinic leadership decided to permit the Oral Torah to be transcribed in writing and disseminated. The verse is interpreted to mean that "It is better that one letter of the Torah [the verse forbidding the writing down of the Oral Torah] should be uprooted than that the whole of the Torah be forgotten." (Gittin 60a-b, Elon Jewish Law 5:1, Louis Jacobs, p.133 trans.)
In the modern period, the dramatic character of the verse again enters the stage. The verse is among those utilized to justify rabbinic innovations in halakhah (Elon Jewish Law 14:3, 14:5). In Enlightenment period Germany, both the Reformers and their Orthodox opponents cite the verse to justify the urgent nature of their actions ("It is time to act for the Lord"). The two conflicting positions see quite different referents for the verse's "they have voided the law" -- the Reformers felt the need to accommodate the growing disinterest in Jewish law, whereas the Orthodox felt that the Reformers themselves were voiding the law.
In an aggadic midrash, the cock sings the verse as a call to work. Ginsburg, Legends of the Jews, I:3
There is an Israeli periodical named after this verse, Et la'asot //trans: "It is time to work (for the Lord)"