Problem: Why would God want to kill Moses, if he selected him to lead his people out of slavery?
Solution: Let’s consider several questions:
Was this a cruel action from God? No. If God really wanted to take Moses’ life, he could have done so at any moment. Instead, he threatened death, so that Moses would make a decision about circumcising his son. Moreover, God has prerogatives over the taking of life that we do not.
Was Moses or Gershom being threatened with death? Some commentators believe that Gershom—not Moses—was the one being threatened by God. While the NIV places Moses’ name in the passage, the pronouns are ambiguous. A good case can be made that God is threatening Gershom’s life—not Moses’ life. For one, the context is referring to God’s firstborn son, Israel (v.22) and Pharaoh’s firstborn son (v.23). Second, the focus of this text is Gershom’s circumcision.
On the other hand, the nearest antecedent for the pronoun “him” in verse 26 would refer to Moses (“He let him alone”). Second, the same language of “met” describes an encounter with Moses in verse 24 and verse 27. Third, Moses was unable (and perhaps too sick?) to circumcise Gershom because he was threatening him with death (v.24). We’re frankly agnostic on this perspective because it doesn’t change our interpretation of this passage very much.
Why was circumcision so important to God? The penalty for refusing circumcision was to be “cut off” from the people (Gen. 17:14). Cole writes, “Circumcision is a symbol of putting away all that is unpleasing to God, and of dedication to God for the task ahead.” This was a central sign that a person was choosing to be a part of God’s people. Refusing to circumcise was a sign of outright rebellion.
Why had Moses and Zipporah not circumcised Gershom? We’re unsure. As the daughter of a Midianite priest, perhaps Zipporah didn’t agree with circumcision, and there was strife Moses’ marriage as a result. This would explain why Zipporah immediately knew what was going on when Moses fell ill. She immediately leaped into action to circumcise Gershom because she knew what was going on.
What is the lesson of this passage? God was likely concerned that Moses was being hypocritical. Moses would later teach others God’s commandments, but he wasn’t following one of the essential commandments himself. Before Moses could get others to follow God, he needed to get himself and his family to follow God. A leader needs to get their household in order before they are ready to serve God (1 Tim. 3:4). Moreover, leaders have higher standards than those not in leadership. Before he was leading, God didn’t bring up this issue with Moses. However, after he stepped forward to lead, this issue became important to God.
 See Douglas K. Stuart, Exodus, vol. 2, The New American Commentary (Nashville: Broadman & Holman Publishers, 2006), 153.
 R. Alan Cole, Exodus: An Introduction and Commentary, vol. 2, Tyndale Old Testament Commentaries (Downers Grove, IL: InterVarsity Press, 1973), 85.
“And it came to pass by the way in the inn, that the Lord met him, and sought to kill him. (Ex 4:24)”