To understand the lineage of John the Baptist, we have to read the Old Testament, 1 Chronicles 24:1-19.
"Now these are the divisions of the sons of Aaron. The sons of Aaron were Nadab, Abihu, Eleazar, and Ithamar. And Nadab and Abihu died before their father, and had no children; therefore Eleazar and Ithamar ministered as priests. Then David with Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, divided them according to the schedule of their service. Now there were more leaders found of the sons of Eleazar than of the sons of Ithamar, and thus they were divided. Among the sons of Eleazar there were sixteen heads of their fathers' houses, and eight heads of their fathers' houses among the sons of Ithamar. Thus they were divided by lot, one group as another, for there were officials of the sanctuary and officials of the house of God, from the sons of Eleazar and from the sons of Ithamar. And the scribe, Shemaiah the son of Nethaneel, one of the Levites, wrote them down before the king, the leaders, Zadok the priest, Ahimelech the son of Abiathar, and the heads of the fathers' houses of the priests and Levites, one father's house taken for Eleazar and one for Ithamar. Now the first lot fell to Jehoiarib, the second to Jedaiah, the third to Harim, the fourth to Seorim, the fifth to Malchijah, the sixth to Mijamin, the seventh to Hakkoz, the eighth to Abijah, the ninth to Jeshua, the tenth to Shecaniah, the eleventh to Eliashib, the twelfth to Jakim, the thirteenth to Huppah, the fourteenth to Jeshebeab, the fifteenth to Bilgah, the sixteenth to Immer, the seventeenth to Hezir, the eighteenth to Happizzez, the nineteenth to Pethahiah, the twentieth to Jehezekel, the twenty-first to Jachin, the twenty-second to Gamul, the twenty-third to Delaiah, the twenty-fourth to Maaziah. This was the schedule of their service for coming into the house of the Lord according to their ordinance by the hand of Aaron their father, as the Lord God of Israel had commanded him. "
Let's read verse 10 again. "The seventh to Hakkoz, the eighth to Abijah. " In the days of King David, there were numerous priests, so there was also a need to establish a regulation for their systematic services. Thus, David assigned lots to each of the sons of Aaron so that the sacrifice was offered in order. (As you all know, Aaron was the older brother of Moses. God ordained Moses as His agent, and Aaron as the High Priest of the Holy Tabernacle before the people of Israel.)
All the other Levites were put under the priests and Aaron and the priests, his sons, took charge of all the sacrifices before God. Before David assigned lots, the priests, who were the descendants of Aaron, had to draw lots each time and it had caused much confusion.
Therefore, David arranged a system by putting each division in order. There were 24 divisions in an order, originating from the grandsons of Aaron, and the eighth was Abijah. It is said, "A certain priest named Zacharias, of the division of Abijah." So Zacharias was a priest of the division of Abijah, and they were both descendants of Aaron the High Priest.
It was Zacharias, a priest of the division of Abijah, who was John the Baptist's father. We know from the Bible that they used to marry within their families.
So, Jacob married his uncle's daughter from his mother's side. It is this explanation of the lineage that has profound importance. It says, "A certain priest named Zacharias, of the division of Abijah. "
Therefore, he was definitely a descendant of Aaron. Who? Zacharias, John the Baptist's father. This is an important fact in explaining the redemption of Jesus, and the ministry of John the Baptist, and the passing of the world's sins onto Jesus.