首くびを洗あらって待まつ

Idiom

1to wait for one's punishment ; to wait before one gets what's coming to one ; to wash one's neck and wait (i.e. for one's beheading) Translated by Jiyomi

expressions (phrases, clauses, etc.) · Godan verb with 'tsu' ending

JMdict entry 2780210. Source and licence.