此女有夫请勿调戏此男有妇请勿勾引
[cĭ nǚ yŏu fū qĭng wù diào xì cĭ nán yŏu fù qĭng wù gōu yĭn]
The phrase means 'Do not flirt with this woman as she is married; do not诱惑this married man.' It’s used by people, typically in a lighthearted way, to indicate that they are committed and off-limits.