Le Deutéronome 31:7 Midrash : Ein Yaakov (Glick Edition) & Sifrei Devarim

It is written (Deut. 31, 7) Thou must go with this people, etc., and it is written (Ib. 23) Thou shalt bring. R. Jochanan said: Moses said to Joshua: "You and the elders shall rule over them;" but the Holy One, praised be He! said: "Thou (alone) shalt rule over them, because there must be one ruler to a generation, and not two rulers."

(Ibid. 28) "And charge (tzav) Joshua": "charging" (tzivui) is prompting to zeal, as it is written (Ibid. 31:7) "And Moses called to Joshua and he said to him before the eyes of all of Israel: 'Be strong and firm'": "Be strong" in Torah, "and be firm" in good deeds.

(Devarim, Ibid. 12) "When you finish tithing": I might think on Channukah; it is, therefore, written here (Ibid. 14:28) "at the end," and elsewhere (Ibid. 31:10) "at the end." Just as "at the end" there signifies a festival, so, "at the end" here signifies a festival. — But why not say, then: Just as "at the end" there signifies the festival of Succoth, so, here, the festival of Succoth is signified! It is, therefore, written (Ibid. 26:12) "When you finish tithing" — the festival when all the tithes have been finished — Pesach. From here they ruled: On the eve of the last day of Pesach of the fourth year and the seventh year, there took place the removal (from the house [biur] of the tithes): on the fourth year, by reason of the poor-tithe of the third year; and on the seventh year, by reason of the poor-tithe of the sixth year. I might think that the (produce of) the seventh year (shemitah), too, is subject to removal; it is, therefore, written (Ibid.) "in the third year," a year which is subject to tithing, excluding the seventh year, which is not subject to tithing. I might think that two tithes both first-tithe and second-tithe (along with poor-tithe) obtain on it (the third year); it is, therefore, written (of the third year), (Ibid.) "the year of the (one) tithe." One tithe obtains on it and not two. I might think that only the poor-tithe, of which the verse speaks, is signified. Whence do I derive the other tithes (for inclusion)? From "all the tithe of your produce."