Biblical Context:
The account of Moses building an altar is found in the Book of Exodus, specifically in Exodus 24:4. This event occurs after the Israelites have been delivered from Egypt and are encamped at the base of Mount Sinai. It is a significant moment in the establishment of the covenant between God and the people of Israel.

Scriptural Reference:
Exodus 24:4 : "And Moses wrote down all the words of the LORD. He got up early the next morning and built an altar at the base of the mountain and set up twelve pillars for the twelve tribes of Israel."

Historical and Theological Significance:
The building of the altar by Moses is a pivotal act in the ratification of the Mosaic Covenant. This covenant is foundational for the identity and religious life of the Israelites. The altar serves as a physical representation of the people's commitment to the covenant and their relationship with God. The twelve pillars symbolize the twelve tribes of Israel, emphasizing the unity and collective responsibility of the nation in upholding the covenant.

Ritual and Worship:
In the ancient Near Eastern context, altars were central to religious worship and sacrificial practices. Moses' construction of the altar is followed by the offering of burnt offerings and peace offerings, as described in Exodus 24:5. These offerings are acts of worship and consecration, signifying the people's dedication to God and their acceptance of His laws.

Covenant Ratification:
The altar is integral to the covenant ceremony. After the offerings, Moses takes the blood of the sacrifices and sprinkles it on the altar and the people, as recorded in Exodus 24:6-8. This act of sprinkling blood is a solemn ritual that seals the covenant, symbolizing purification and the binding nature of the agreement between God and Israel.

Symbolism and Typology:
From a theological perspective, the altar built by Moses prefigures the ultimate sacrifice of Jesus Christ in the New Testament. The blood of the covenant, as mentioned in Exodus 24:8, foreshadows the new covenant established through Christ's sacrificial death, as referenced in the New Testament (Hebrews 9:18-22).

Moses' Role:
Moses acts as the mediator between God and the Israelites. His role in building the altar and conducting the covenant ceremony underscores his leadership and prophetic office. Moses' actions demonstrate obedience to God's commands and his dedication to guiding the people in their spiritual journey.

Implications for Israel:
The building of the altar and the subsequent covenant ceremony mark a defining moment for the Israelites. It establishes their identity as God's chosen people and sets the framework for their societal and religious laws. The covenant at Sinai, with the altar as its focal point, becomes the foundation for Israel's relationship with God throughout their history.

Conclusion:
The account of Moses building an altar is a profound moment in biblical history, rich with theological meaning and significance for the covenant relationship between God and His people.