George Haydock's Catholic Bible Commentary - Matthew 12:40
In the whale's belly. [4] The word signifies a great fish, and was not perhaps that which we commonly call a whale. In the prophet Jonas, it is called, a great fish. --- Three days and three nights; not three whole days and three nights, but part of three natural days, from which, in common computation, the nights used not to be separated. We have an instance of this, Esther iv. 16, where the Jews were ordered to fast with her three days, and three nights: and yet (Chap. v, ver. 1) Esther,... read more
Hawker's Poor Man's Commentary - Matthew 12:38-45
"Then certain of the scribes and of the Pharisees answered, saying, Master, we would see a sign from thee. (39) But he answered and said unto them, An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas: (40) For as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth. (41) The men of Nineveh shall rise in judgment with this... read more