When the spring silkworm dies, the silk will be exhausted, and the wax torch will turn to ashes and the tears will begin to dry
Silk will be exhausted: Silk is a homophone for "Si", and "Silk will be exhausted" means unless it dies. , the longing will end.
The tears begin to dry: Tears refer to the candle oil when burning. This is a pun, referring to the tears of lovesickness.