Р327
СЛОЖА РУКИ сидеть, less often ждать, стоять и т. п.
collVerbal AdvInvaradvfixed WO (to be) idle, inactive ( usu. when the situation requires some decisive, energetic action): (be) sitting on one's hands
(be sitting around (about)) twiddling one's thumbs(be sitting around) doing nothing(be sitting) idly by.
the corresponding modern form is the perfective verbal adverb «сложив».