# The one who says

"Anyone who says" or "The person who says"

# I know God

"I have a good relationship with God"

# does not keep

"does not obey" or "disobeys"

# his commandments

"what God tells him to do"

# the truth is not in him

The truth is spoken of as if it were an object that could be inside the believers. Alternate translation: "he does not believe what God says is true"