Rashi on Deuteronomy 20:5/רש"י על דברים כ׳:ה׳

1ולא חנכו [WHAT MAN IS THERE THAT HATH BUILT A NEW HOUSE] AND HATH NOT DEDICATED IT — i.e. has not yet dwelt in it. The term חנך denotes beginning a thing (here, it means beginning to live in it; cf. Rashi on Genesis 14:14).

2ואיש אחר יחנכנו [LEST HE DIE IN THE WAR] AND ANOTHER MAN DEDICATE IT — which is a matter that causes grief of mind.