TT #285 · Parashas Shoftim · Seventh Aliyah · Passuk 20:05
And the officers shall speak to the people, saying: Who is the man who has built a new house and has not dedicated it? Let him go and return to his house, lest he die in the battle and another man dedicate it.
Torah Temimah points to Sotah 43a.
TT lemma: וְלֹא חֲנָכוֹ.
English: ‘And has not dedicated it’ – that he has not yet dwelt in it.
Derash defining dedication (Bavli) — the exemption lasts until the owner has begun to live in the house.
Until the builder has taken up residence in the new house, he is exempt from going out to war.