I playfully tell people that I grew up in a “confused Mennonite home.” My father was a pastor in the Mennonite church and, unlike the vast majority of Mennonites, was committed to the doctrines of grace or what are often called the five points of Calvinism. My parents loved the ministry of R. C. Sproul and Ligonier and would attend Reformed conferences with joy and much agreement. Espousing, adoring, and preaching the doctrines of God’s sovereign grace in a Mennonite context came at a cost for my father who was sometimes met with resistance. I’m proud of my father for faithfully contending for the unshakable truths of God’s sovereignty.
I also tell people that I studied my way out of the Mennonite faith. By college, I already had the doctrines of grace embedded in my theology, but it was in the last year of my studies at Reformed Presbyterian Theological Seminary that I finally embraced Covenant or Reformed Theology. It was ultimately a journey to Covenant Theology, but it was Dr. Richard Gamble’s lecture on circumcision that finally pushed me over the line. And from that point on, I began to understand more deeply the troubles within Mennonite theology.
One massive problem with Menno Simons’ thinking, a problem I think many Mennonites today don’t know about or agree with, was his Christology. Many considered Menno a heretic for his view of Jesus Christ. Menno embraced a doctrine often labeled “celestial flesh.” Menno believed that Jesus Christ did not take on human flesh and blood from Mary but instead possessed a heavenly flesh. Menno said:
Christ Jesus remains the precious blessed fruit of the womb of Mary, according to the words of Elisabeth, conceived not of her womb but in her womb, wrought by the Holy Spirit through faith, of God the omnipotent Father, from high heaven. 
If you read it quickly, that sounds right. The problem is in the words “not of her womb but in her womb.” Menno also said:
Christ Jesus, as to His origin, is no earthly man, that is, a fruit of the flesh and blood of Adam. He is a heavenly fruit or man. For His beginning or origin is of the Father (John 16:28), like unto the first Adam, sin excepted. 
No earthly man? So, though preserving the divinity of Jesus Christ and his virgin birth, and though preserving some unique kind of humanity of Jesus Christ, Menno rejected the long-established Christology of the church articulated in the ecumenical creeds (e.g. Chalcedonian Creed). To this point, Egil Grislis states:
Despite some inner tensions, Menno’s over-all Christological position obtains its basic coherence by centering attention on the heavenly origins of the flesh of Christ. As has been pointed out by Cornelius Krahn, the traditional single miracle of a fatherless birth has now been intensified to a double miracle: Christ is without a human father and mother! 
Menno’s doctrine of Christ strikes at the very core of our faith, at the comfort we receive from the incarnation. I’ll explain that in a bit, but I find the writings of another well-known figure to be just as problematic, probably more. Many would consider this man a heretic as well.
In his book Velvet Elvis, Rob Bell presents a dangerous argument questioning historic and ecumenical Christology. You can read the argument yourself on page 26 of Velvet Elvis, but here’s a summary. Bell believes that a person can reject the virgin birth and still be a Christian and love God. He introduces a hypothetical and blasphemous illustration where archeologists prove through DNA samples that Jesus Christ actually had an earthly father named Larry. He also includes a crafty illustration casting doubt on the meaning of virgin in Scripture. And Bell means to suggest by the illustration that the Christian faith does not fall apart if we question or deny doctrines such as the virgin birth. I wholeheartedly disagree with Bell’s thinking. If Christ did not assume Mary’s flesh and if Mary was not actually a virgin, all of the Bible falls and with it our salvation. The two natures of Christ are integral to our salvation and comfort in life and death.
Mennonites and progressive Christians don’t tend to be confessional. I think there is great safety and comfort in being confessional, in anchoring to a faithful and time-tested articulation of the Christian faith. I think the Apostles’, Nicene, Athanasian, and Chalcedonian Creeds and catechisms like the Heidelberg and Westminster Shorter Catechisms protect us from theological drift and novelty. They anchor us to historic Christianity. I think the further people get from confessional Christianity the more susceptible they are to falling into age-old heresies. Church history can teach us invaluable lessons. Hasn’t that proven true?
Today, we come to Heidelberg 35. It says this:
What do you confess when you say “He was conceived by the Holy Spirit, born of the virgin Mary”? The eternal Son of God, who is and remains true and eternal God, took upon Himself a true human nature from the flesh and blood of the virgin Mary through the working of the Holy Spirit. Thus He is also the true seed of David and like his brothers in every respect, yet without sin.
That right there is what Christians believe about Christ Jesus the Lord. It’s clear. It’s concise. It’s profound. It’s entirely Biblical.
The incarnation changed nothing about the divinity of the Son of God. The Son of God remained true and eternal God. But, the eternal Son of God did take “upon Himself a true human nature from the flesh and blood of the virgin Mary.” The Westminster Confession of Faith 8:2 says:
The Son of God, the second person of the Trinity, being very and eternal God, of one substance and equal with the Father, did, when the fullness of time had come, take upon Him man’s nature, with all the essential properties, and common infirmities of a man, yet without sin; being conceived by the power of the Holy Spirit, in the womb of the virgin Mary, of her substance. So that two whole, perfect, and distinct natures, the Godhead and the manhood, were inseparably joined together in one person, without conversion, composition, or confusion. This person is very God, and very man, yet one Christ, the only Mediator between God and man. 
The historic witness of the church is unified. Jesus Christ is of the substance of Mary and is the only Mediator between God and man.
Now, how is this connected to our comfort in life and death? Well, consider Heidelberg 14. No mere creature can pay for our sins. Consider Heidelberg 15. The mediator must be true and righteous man and at the same time true God. Consider Heidelberg 16. If Jesus is not true man, if he didn’t take upon himself flesh and blood from Mary, if he had an earthly father and was therefore sinful, he cannot satisfy God’s justice and pay for our sins. But because Jesus Christ is true and righteous man who took upon himself true flesh and blood from the virgin Mary while remaining true God, he is sufficient as our Mediator to cover our sin and reconcile us to God. His conception by the Holy Spirit, virgin birth, innocence, and perfect holiness all confirm for us that Jesus Christ is the only true Mediator who can reconcile us to God. As we trust in Christ alone, we are confident and should have no doubt that Christ has paid for all our sins, we are righteous in God’s sight, and we possess the undying love of God in Christ. Brothers and sisters, theology matters. What you believe matters. Your salvation and comfort depend on Jesus Christ being the Son of God, one person with two distinct natures.
 Egil Grislis, “The Doctrine of Incarnation According to Menno Simons,” Journal of Mennonite Studies Vol. 8 (1990). file:///C:/Users/shirk/Desktop/656-Article%20Text-656-1-10-20090508%20(1).pdf
 The Confessions of Our Faith, Fortress Edition, ed. Rev. Brian W. Kinney (Fortress Book Service & Publishers, 2007), 124. Italics mine.
Quotes from the Heidelberg Catechism and creeds are taken from Zacharias Ursinus & Jonathan Shirk, The Heidelberg Catechism: True Comfort for Life & Death (Manheim: Small Town Theologian, 2021).
Scripture quotations are from the ESV® Bible (The Holy Bible, English Standard Version®), copyright © 2001 by Crossway, a publishing ministry of Good News Publishers. Used by permission. All rights reserved. May not copy or download more than 500 consecutive verses of the ESV Bible or more than one half of any book of the ESV Bible.