And when he had fasted forty days..... As Moses did, when he was about to deliver the law to the Israelites, Ex 34:28 and as Elijah did, when he bore his testimony for the Lord of hosts,1Ki 19:8 so did Christ, when he was about to publish the Gospel of his grace, and bear witness to the truth.
"Forty nights" as well as days, are mentioned; partly to show that these were whole entire days, consisting of twenty four hours; and partly to distinguish this fast of Christ from the common fastings of the Jews, who used to eat in the night, though they fasted in the day: for according to their canons , they might eat and drink as soon as it was dark, and that till cock crowing; and others say, till break of day.
Maimonides says, they might eat and drink at night, in all fasts, except the ninth of Ab. What is very surprising in this fasting of our Lord, which was made and recorded, not for our imitation, is, that during the whole time he should not be attended with hunger; for it is added,he was afterwards an hungered; that is, as Luke says, "when" the "forty" days "were ended", Lu 4:2 which seized upon him, and is related, both to express the reality of his human nature, which though miraculously supported for so long a time without food, and insensible of hunger, yet at length had appetite for food; and also that very advantageous opportunity Satan had to attack him in the manner he did, with his first temptation.
T. Bab. Taanith, fol. 12. 1, 2. Misn. Taanith, c. 1. sect. 5. Hilch. Taanith, c. 5. sect.