Then understood the disciples that he spake unto them of John the Baptist.
Then the disciples understood that he spake unto them of John the Baptist.
Then the disciples understood that He spoke to them about John the Baptist. [Mal. 4:5.]
Then the disciples realized he was telling them about John the Baptist.
Then the disciples understood that he had spoken to them about John the Baptist.
Then the disciples understood, that he had spoken to them of John the Baptist.