The sidra deals in detail with the fire on the altar. According to rabbinic teaching (Talmud, Yoma 21b), there was fire that came from Above as well as fire that was lit on earth with flames that danced upwards.
Looked at homiletically, this tells us that man and God, earth and heaven, constantly yearn for one another. Man is nothing without God; whilst God, for His part, has a need for man. Otherwise He is a king without a kingdom, a ruler without subjects, a teacher without pupils, a doctor without patients, a lawyer without clients.
Biblical history is the account of the sometimes uneasy relationship between them. God is often disappointed in man; man has his moments when he feels disappointed in God. The ideal is for both parties to the eternal covenant to work together and seek to satisfy each other, the model being the story in Exodus chapter 19 of God descending, as it were, upon Mount Sinai and Moses ascending to the sphere of the Divine.