2 Timothy 2:19…Nevertheless the foundation of God standeth sure, having this seal, The Lord knoweth them that are his.
God knows those – who are His. God puts His seal on those who are redeemed.
Ephesians 1:13…In whom ye also trusted, after that ye heard the word of truth, the gospel of your salvation: in whom also after that ye believed, ye were sealed with that holy Spirit of promise
God’s seal of approval shows that a man is forgiven of sin and cleansed from iniquity. God does not approve nor put His seal on sinful conduct or sinful practice.