平声
level or even tone; first and second tones in modern Mandarin
平生不做亏心事,半夜敲门心不惊
He who never wrongs others does not fear the knock in the night.; Rest with a clear conscience.
太平盛世
peace and prosperity (idiom)
押平声韵
to restrict to even tone (i.e. final rhyming syllable must be classical first or second tone 平聲|平声)