This line begins a clause meaning that Mexico’s eternal destiny is in heaven. The idea is not just political; it is written in a religious and providential tone, suggesting that the nation’s fate has a sacred or divinely guided quality.

Cielo means “heaven” or “sky,” depending on context. Eterno means “eternal,” and destino means “destiny” or “fate.” In context, tu eterno destino refers to the homeland’s eternal destiny. The thought is completed by the next line, which says that this destiny was written by the finger of God.