Keeping rules and being an Israelite are not enough…

Now John wore a garment of camel’s hair and a leather belt around his waist, and his food was locusts and wild honey. Then Jerusalem and all Judea and all the region about the Jordan were going out to him, and they were baptized by him in the river Jordan, confessing their sins. But when he saw many of the Pharisees and Sadducees coming to his baptism, he said to them, “You brood of vipers! Who warned you to flee from the wrath to come? Bear fruit in keeping with repentance. And do not presume to say to yourselves, ‘We have Abraham as our father,’ for I tell you, God is able from these stones to raise up children for Abraham. Even now the axe is laid to the root of the trees. Every tree therefore that does not bear good fruit is cut down and thrown into the fire. “I baptize you with water for repentance, but he who is coming after me is mightier than I, whose sandals I am not worthy to carry. He will baptize you with the Holy Spirit and fire. His winnowing fork is in his hand, and he will clear his threshing floor and gather his wheat into the barn, but the chaff he will burn with unquenchable fire.” (Matthew 3:4–12)

John preached the same message as the OT prophets, a message that needs to be continually preached. The religious people of today fall into the same error — faith is not about outward actions that appear to be keeping God's law; it is about having a heart and life changed by the power of the indwelling Holy Spirit. Nor is it about being in a family or a culture of people who have real faith or this outward behavior testimony typical of false teachers.

But God’s firm foundation stands, bearing this seal: “The Lord knows those who are his,” and, “Let everyone who names the name of the Lord depart from iniquity.” (2 Timothy 2:19)

He knows the heart. If a person claims faith and continues a life of sin, they do not belong to God. 

Lord Jesus, You know who are Your people. At times I might discern wrongly, but eventually Your godliness will show up in those who are, and You will bless all of them. Otherwise, there is still that invitation to repent and receive You as the only One who can change our lives and save us from our sinful selves.