此女有夫请勿诱惑此男有妻请勿勾引
[cĭ nǚ yŏu fū qĭng wù yòu huò cĭ nán yŏu qī qĭng wù gōu yĭn]
This means 'she is married so please do not tempt her / he is married so do not entice him.' It serves as a warning or disclaimer against romantic overtures towards someone who is already in a committed relationship.