Jesus gave two answers. First, he corrected the Sadducees because they did not understand the Scriptures (the Old Testament). The resurrection of the dead is shown most clearly in the Prophets (Isaiah 26:19; Ezekiel 37:1–14) and the Writings (Job 19:26; Psalms 16:9–11; 49:15; 73:23–26; Daniel 12:2). But the Sadducees accepted only the Torah (Genesis, Exodus, Numbers, Leviticus, and Deuteronomy). So Jesus answered them from the Torah.
God called himself “the God of Abraham, the God of Isaac, and the God of Jacob” (Exodus 3:6, 15–16). This showed that God’s covenant (binding relationship) with the patriarchs could not be ended by death. Abraham, Isaac, and Jacob were still alive to God (Matthew 8:11–12; 13:17; Luke 16:19–31; John 8:56). God is the God of the living, not the dead. This means that God’s relationship with his people continues after physical death.
Second, Jesus corrected the Sadducees because they did not understand God’s power. They thought resurrection life would be the same as mortal life. But resurrection life is new and different. In that life, people will not need sexual reproduction because there will be no more death. Marriage will no longer have the same role. Believers will share full fellowship with God and with all God’s people (Mark 10:29–30; Matthew 19:28–29; Luke 18:29–30; Revelation 21:1–4). In this way, resurrected believers will be like the angels in heaven.
The answer Jesus gave shows his wisdom before his opponents. It also confirmed the hope of resurrection for his followers. Jesus is "the resurrection and the life" (John 11:25). He has defeated death. He promises that all who believe in him will "not perish but have eternal life" (John 3:16).