TT #299 · Parashas Shoftim · Seventh Aliyah · Passuk 20:07
And who is the man who has betrothed a woman and has not taken her? Let him go and return to his house, lest he die in the battle and another man take her.
Torah Temimah points to Sotah 43a / Sifrei.
TT lemma: אֲשֶׁר אֵרַשׂ אִשָּׁה וְלֹא לְקָחָהּ.
English: ‘Who has betrothed a woman and has not taken her’ – he shall return.
Derash on the betrothal exemption (Bavli / Sifrei) — the unfinished marriage frees him from combat.
A man who has betrothed a woman but has not yet taken her into his house is sent home from the battle lines.