Why does the Torah insert the word "Asher Eiras Ishah"?
Sotah, 44a: To incorporate in the current Halachah someone who betrothed a woman, irrespective as to whether she is a virgin, a widow or if she is a Shomeres Yavam - and even if there were five brothers and one of them died, they are all sent home. 1
See Torah Temmah, note 33, who learns it from the word "Ishah" - like the Yerushali in the following D'rashah.
What are the implications of the word "Ishah"?
Yerushalmi Sotah, 5:6: It implies that he is sent home, even if he is a Bachur who betrothed a widow or a widower who betrothed a virgin. 1
See Torah Temimah, note 34, who discusses a widower who betrothed a widow and divorcee who remaried his ex-wife.
What are the implications of the suffix "ve'Lo Lekachah"
Sotah, 44a: It comes to preclude a Kohen Gadol who betrothed a widow, a Kohen Hedyot who betrothed a Gerushah or a Chalutzah and a Yisrael who betothed a Mamzers and a Nesinah, who are not sent home from the battle-front. 1
See Torah Temimah, note 35.
Why does the Torah add the (otherwise superfluuous) words "ve'Ish Acher Yikachenah"?
Kidushin, 13b: To teach us that the death of her husband permits a woman to remarry. 1
Refer to 20:5:5:1.
What is the significance of the order in which the Pasuk presents the first three groups of soldiers who are obligated to return home?
Sotah, 44a: It teaches us Derech Eretz - that a man should first build a house and plant a vineyard before getting married. 1
Be'er-Sheva (44a): Presumably, the Torah is also specific regarding the house preceding the vineyard. However, the Gemara, and also the Pasuk in Mishlei 24:27 cited there to support this, writes 'afterwards' only regarding marriage, This requires investigation. The Rambam (Hilchos De'os 5:1) rules that Parnasah precedes building a house! Divrei Rivos (230)
What should a person do if he can only afford one of the three things?
Maharsha (in Sotah, 44a): He may do whichever one suits him best. 1
See Torah Temimah, note 31, who elaborates.
Why might the above-mentioned groups die if they do not go home?
Rashi: Because if they disobey the Kohen's 1 orders to return home, they deserve to die.
Ramban #1 (in Pasuk 8, according to R. Yossi ha'Gelili): One who sinned is afraid. He thinks that his sins may cause him to fall in battle. The Torah is covering up for him
What is the difference between the soldiers who are sent home from the battle-front, and a Chasan during his first year of marriage, whom the Torah (24:5) forbids to go to war for the entire first year after his wedding?
Rashi (in Ki Seitzei, 24:5): The Chasan during his first year of marriage 1 may not leave his house for anything connected with war, neither to provide the army with water and food, nor to prepare the roads (sappers), whereas all those whom the Kohen sends back from the front ... are still required to provide water and food and to prepare the roads.
Rashi (Ibid.): And the same applies to someone who redeemed his Kerem R'vai and someone who
