Du Fu has a precious poem about letters from home. What is this poem?

This is Du Fu's patriotic poem: "A letter from home is worth a ton of gold."

Du Fu in Spring

Chang' an fell, the country was broken, and only the mountains and rivers remained; Spring has come, and the sparsely populated Chang' an city is densely forested.

Sad state, can not help but burst into tears, amazing birds, leaving sorrow and hate.

At the peak of March, a letter from home is worth a ton of gold.

Twisting with melancholy, scratching my head and thinking, the more I scratch my white hair, I can hardly insert a hairpin.