The taxation. The birth of Jesus at Bethlehem.
Verse 5 ... To be taxed with Ma'ry ... his espoused wife, being great with child.
Matthew 1:18 ... (The virgin Mary, while espoused to Joseph, conceived by the Holy Ghost.) Now the birth of Jesus Christ was on the wise: When as his mother Ma'ry was espoused to Jo'seph, before they came together, she was found with child of the Holy Ghost.
Luke 2:6 ... And so it was, that, while they were there, the days were accomplished that she should be delivered.
Luke 2:7 ... And ... she brought forth her firstborn son, & wrapped in swaddling clothes, & laid him in a manager; because there was no room for them in the inn.
Matthew 1:18 ... (The birth of Jesus.) And knew her not till she had brought forth her firstborn son: & he called his name JESUS.
Scripture reference used from The KJV Bible, SouthWestern Co., Nashville, TN