他爱她深入骨髓她爱他至死不渝
[tā ài tā shēn rù gú suĭ tā ài tā zhì sĭ bù yú]
It describes an intensely mutual love between two people: 'He loves her deep into his bones and she loves him till death does them part.' It symbolizes an unshakable, enduring love for each other.