Why did God send Jesus when He did? What is the fullness of time?

from the old testament

• God intentionally worked in human history to prepare for the sending of Jesus at just the right time. In the Old Testament, we see God's sovereign hand at work, such as when He sent Joseph to Egypt just before a great famine (Genesis 41:46-47), ensuring that the Israelites would grow into a mighty nation during their time in Egypt (Exodus 1:7). God also orchestrated the timing of Israel's struggles with foreign nations, allowing for moments of judgment and correction for His people (Judges 2:16-18). He arranged for Esther, a Jewish girl, to become queen and save her people from genocide (Esther 4:14), highlighting God's providence in times of peril. Living outside of time, God saw all of history and orchestrated these events to prepare for the ultimate plan of salvation through Jesus Christ.
• The world needed to understand why we need Jesus. That was the purpose of the Old Testament law. The law revealed God's holiness and humanity's sinfulness (Leviticus 11:44-45). It also pointed to the need for atonement, demonstrated through sacrifices like the scapegoat in Leviticus 16:21-22.
• God also pursued His people to be a light to the world, pointing others to Him (Genesis 12:1-3). For generations, God blessed, disciplined, cajoled, and pled with the Israelites to follow His will and accept His goodness. He promised blessings for obedience (Deuteronomy 28:1-2) and warned of destruction for disobedience (Deuteronomy 28:15). Despite His faithfulness and the execution of both blessings and judgments, they were unable to remain faithful (Judges 2:11-19). If we could have been made right with God on our own, we never would have appreciated His sacrifice. A gift is most readily accepted when it's something we can't get for ourselves.
• Daniel 9:24-26 must have sounded strange when Gabriel gave the message. The Jews were given seventy weeks (groups of seven years) to finish rebelling and return to God. The starting point was the decree to restore and build Jerusalem. Sixty-nine weeks later, "an anointed one shall be cut off and shall have nothing" (Daniel 9:26). The command to rebuild Jerusalem was given in 445 BC (see Nehemiah 2:5). Scholars place Christ's triumphal entry into Jerusalem exactly sixty-nine "weeks"—or 483 years—later. God's plan was so precise He let Daniel know five hundred years in advance. It's believed that Daniel's prophecy then told the wisemen when to show up to celebrate Jesus' birth.

from the new testament

• Galatians 4:4 says, "But when the fullness of time had come, God sent forth his Son, born of a woman, born under the law." We don't exactly know what "the fullness of time" refers to, but God has allowed us these few hints. Most striking, God did not wait around until things looked right. Having seen all of human history, He predicted exactly when Jesus would come.
• Paul reveals that the Old Testament law prepared us for Christ: "Therefore the law was our tutor to bring us to Christ, that we might be justified by faith" (Galatians 3:24). Ultimately, the law pointed forward to the sacrifice of Christ, which would fulfill what the law could not (Hebrews 10:1-4).
• Along with the preparations of the Old Testament, society was also ready for God to send Jesus. In the time of Jesus' life, Rome, Greece, Babylon/Persia, and Egypt were relatively peaceful, having come to a cessation of the major hostilities that had plagued the area for centuries. This meant travel was fairly easy (Acts 16:6-10). Wars were minimal, so resources could be devoted to culture, philosophy, and education (Acts 17:21). A singular culture—Greek—spread across the region, ensuring most people understood a common language (Acts 21:37-40), and even the adherents of the most far-fetched religion (Judaism) were familiar enough with the reigning philosophy that meaningful communication was possible (Acts 17:22-23).
• The region was also spiritually hungry. The ineffectiveness of the Roman gods was becoming more and more evident. The claustrophobic Roman rule kept Jews on the look-out for the promised Messiah to deliver them. And individuals were seeking for something better in their own lives, beyond the state and the state-ordained religions. Even a Samaritan woman, rejected by Jews for her nationality and her gender, was eagerly awaiting the Messiah (John 4:25).

implications for today

God is the God who works through human history, intricately weaving His plans into the fabric of time. Jesus' arrival on Earth was not a random event but a moment carefully pre-ordained and divinely orchestrated from the beginning of time. His birth was not only prophesied but also strategically timed, coming at the precise moment in history when the world was ready to hear and understand His message. The Roman Empire's dominance provided roads for travel, a common language for communication, and a framework for the spread of the gospel, all of which were part of God's grand design. Jesus' life, death, and resurrection were not only essential for our salvation but also revealed God’s profound love and purpose for humanity. After Jesus' ascension, the situation proved custom-made for the spread of the gospel. The sack of Jerusalem in AD 70, although tragic to the Jewish people, caused hundreds of Christ-followers to escape to Asia, Africa, and Europe to spread their beliefs. They influenced Gentiles, who in turn joined the Roman army and took the gospel to places as far away as Britain. The persecution of Christians by the Roman government had a similar effect, both strengthening the faith of believers and leading them to flee with the message of Christ. If God could meticulously arrange such a pivotal moment in history for our redemption, we can rest assured that He is in control of every detail of our own lives and that He loves us immensely. Trusting Him with our lives, knowing He is sovereign over time and eternity, is not only reasonable but essential to living with peace and purpose.