Tosefta zu Jechezkiel 45:78

[When] Rosh Chodesh Adar falls on Shabbat, we read the portion of "Shekalim" (Ex. 30:11-16) and in addition we read the portion of the shekalim that concerns Yehoyada the Kohen (commencing with 2 Kings 12:8). What is the "first Shabbat"? Any Rosh Chodesh Adar falls within [that designation], even on Erev Shabbat. On the second Shabbat, [we read the portion beginning] "Remember [what Amalek did]" (Deut. 25:17) and additionally we read "Thus said the Lord of Hosts, I remember what Amelek did to Israel" (1 Sam. 15:2). What is the "second Shabbat"? Every [Shabbat] in which Purim falls within it, and even on Erev Shabbat. On the third [Sabbath we read the portion of] the Red Heifer, and additionally we read "And I will sprinkle pure water on you and you will be purified" (Ezek. 36:25). What is the "third Shabbat"? Any [Shabbat] that immediately follows Purim. The fourth [Shabbat we read], "This month shall be to you the head of the months" (Ex. 12:2), and in addition [we read] "Thus said the Lord, in the first [month], on the first of the month" (Ezek. 45:18). Which is the fourth Shabbat? Any [Shabbat] in which Rosh Chodesh Nissan falls within it, and even on Erev Shabbat.

Said Rabbi Yosei, how do we know that terumah is one in fifty? As it is said (Num. 31:30), "And from the half-share of the Children of Israel you are to take one, withheld from the fifty," [and therefore] even that which I (i.e., God) apportioned to you in another place, behold, just as there it is one in fifty, so too here it is one in fifty. How do we know that if we take terumah and [only] one in sixty come into our hands, that our terumah is [valid] terumah? As it is said (Ezek. 45:13), "This is the contribution you shall make: One-sixth of an ephah from every chomer of wheat and one-sixth of an ephah from every chomer of barley" (an ephah is one-tenth of a chomer, and thus a sixth of an ephah is one sixtieth of a chomer). Rabbi Yishmael [son of Rabbi Yosei] says, it is [derived] from the cities of the Levites. [Note: Per Minchat Bikkurim, Rabbi Yishmael alludes to the proportion of 1 in 30, the approximate ratio of Levites (23,000, see Num. 26:62) to the remaining tribes (601,730, see Num. 26:51) before entering the Land of Israel.]