In that night - The night is thus clearly distinguished from the evening when the lamb was slain. It was slain before sunset, on the 14th, and eaten after sunset, the beginning of the 15th.
With fire - Among various reasons given for this injunction the most probable and satisfactory seems to be the special sanctity attached to fire from the first institution of sacrifice (compare Genesis 4:4).
And unleavened bread - On account of the hasty departure, allowing no time for the process of leavening: but the meaning discerned by Paul, 1 Corinthians 5:7-8, and recognized by the Church in all ages, was assuredly implied, though not expressly declared in the original institution. Compare our Lord’s words, Matthew 16:6, Matthew 16:12, as to the symbolism of leaven.
Bitter herbs - The word occurs only here and in Numbers 9:11, in reference to herbs. The symbolic reference to the previous sufferings of the Israelites is generally admitted.