Introduction:
The phrase "lights in the expanse of the sky" refers to the celestial bodies created by God as described in the Book of Genesis. These lights serve specific purposes, including marking time and seasons, and providing light to the earth. This entry explores the biblical account of their creation, their functions, and their significance within the biblical narrative.

Biblical Account:
The creation of the lights in the expanse of the sky is detailed in Genesis 1:14-19. On the fourth day of creation, God said, "Let there be lights in the expanse of the sky to distinguish between the day and the night, and let them be signs to mark the seasons and days and years" (Genesis 1:14). God made two great lights—the greater light to govern the day and the lesser light to govern the night. He also made the stars. These celestial bodies were set in the expanse of the sky to give light on the earth, to govern the day and the night, and to separate light from darkness.

Functions and Purposes:
1. Separation of Day and Night: The greater light, identified as the sun, governs the day, while the lesser light, the moon, governs the night. This separation establishes a natural rhythm of time, providing a framework for human activity and rest.

2. Signs and Seasons: The lights serve as signs to mark sacred times, seasons, days, and years. This function is crucial for the establishment of calendars and the observance of religious festivals and agricultural cycles.

3. Illumination: The primary purpose of these lights is to provide illumination for the earth. The sun's light is essential for life, supporting photosynthesis and regulating the earth's climate. The moon and stars provide light during the night, offering guidance and navigation.

4. Governance: The celestial bodies are described as governing the day and night, indicating their role in maintaining order and stability in the natural world.

Theological Significance:
The creation of the lights in the expanse of the sky underscores God's sovereignty and creative power. By speaking these celestial bodies into existence, God demonstrates His authority over the cosmos. The orderly arrangement of the sun, moon, and stars reflects the divine order and purpose inherent in creation.

The lights also serve as a testament to God's provision and care for His creation. By establishing a system to mark time and seasons, God provides for the needs of humanity, ensuring that life on earth can flourish within the cycles He ordained.

Symbolism and Imagery:
Throughout the Bible, the sun, moon, and stars are used symbolically to convey various theological truths. The sun often represents God's glory and righteousness, as seen in passages like Psalm 84:11, "For the LORD God is a sun and shield." The moon and stars are sometimes used to illustrate God's faithfulness and the enduring nature of His covenant, as in Jeremiah 31:35-36.

Conclusion:
The lights in the expanse of the sky are integral to the biblical understanding of creation. They not only fulfill practical functions but also carry deep theological significance, pointing to the Creator's wisdom, power, and care for His creation.