From December 20-22 Jupiter and Saturn will be so close together that they will appear as a single point of light. The last time this occurred during nightfall was 1226. While minor alignments between the planets occur every 20 or so years, it is extraordinarily rare that they are seen as a single illumination.
It was referenced in Matthew 2:9 “After they had heard the king, they went on their way, and the star they had seen when it rose went ahead of them until it stopped over the place where the child was.”
NASA instructs us to look for the star in the southwest shortly after dusk