Biblical Context:
The narrative of Jacob erecting an altar is a significant event in the patriarchal history of Israel, reflecting themes of covenant, worship, and divine encounter. This event is primarily recorded in the Book of Genesis, where Jacob, the grandson of Abraham, plays a pivotal role in the unfolding of God's promises to the patriarchs.

Scriptural References:
The key passages concerning Jacob erecting an altar are found in Genesis 33:18-20 and Genesis 35:1-7. These passages highlight Jacob's journey, his encounters with God, and his response through acts of worship.

Genesis 33:18-20 :
"After Jacob had come from Paddan-aram, he arrived safely at the city of Shechem in the land of Canaan, and he camped in front of the city. The plot of ground where he pitched his tent he purchased from the sons of Hamor, Shechem’s father, for a hundred pieces of silver. There he set up an altar and called it El-Elohe-Israel."

Genesis 35:1-7 :
"Then God said to Jacob, 'Arise, go up to Bethel and settle there. Build an altar there to the God who appeared to you when you fled from your brother Esau.' So Jacob told his household and all who were with him, 'Get rid of the foreign gods that are among you. Purify yourselves and change your garments. Then let us arise and go up to Bethel, where I will build an altar to God, who answered me in my day of distress. He has been with me wherever I have gone.' So they gave Jacob all their foreign gods and the earrings in their ears, and Jacob buried them under the oak near Shechem. As they set out, a terror from God fell over the surrounding cities, so that they did not pursue Jacob’s sons. So Jacob and everyone with him arrived in Luz (that is, Bethel) in the land of Canaan. There Jacob built an altar, and he called the place El-Bethel, because it was there that God had revealed Himself to Jacob as he fled from his brother."

Theological Significance:
1. Covenant and Worship: Jacob's erection of altars signifies his acknowledgment of God's covenant promises and his commitment to worship the Lord. The altars serve as physical reminders of divine encounters and commitments made between God and Jacob.

2. Divine Encounter and Response: The altars at Shechem and Bethel mark significant moments of divine encounter. At Shechem, Jacob acknowledges God's protection and provision by naming the altar "El-Elohe-Israel," meaning "God, the God of Israel." At Bethel, the altar commemorates God's faithfulness and Jacob's vow to serve the Lord, as Bethel was the site of Jacob's earlier vision of the ladder reaching to heaven (Genesis 28:10-22).

3. Purification and Renewal: Before erecting the altar at Bethel, Jacob instructs his household to purify themselves and discard foreign gods. This act of purification underscores the importance of holiness and exclusive devotion to the God of Israel, reflecting a renewal of commitment to the covenant.

4. God's Faithfulness: The narrative emphasizes God's unwavering faithfulness to Jacob, despite his past struggles and fears. God's command to return to Bethel and the subsequent divine protection highlight His sovereign care and the fulfillment of His promises.

Historical and Cultural Context:
In the ancient Near Eastern context, altars were central to religious practice, serving as sites for sacrifices and offerings. Jacob's actions align with the broader cultural practice of erecting altars to honor deities, yet they distinctly affirm the worship of Yahweh, the one true God of Israel.

Legacy and Impact:
Jacob's altars at Shechem and Bethel have enduring significance in biblical history. They symbolize the establishment of Israel's worship practices and the patriarchal legacy of faith. These sites later become important locations in Israel's religious landscape, with Bethel, in particular, playing a prominent role in the history of the northern kingdom.