Numbers 9:11

The fourteenth day of the second month at even they shall
keep it
The mouth Ijar, as the Targum of Jonathan, which answers to part of our April and part of May; so that there was a month allowed for those that were defiled to cleanse themselves; and for those on a journey to return home and prepare for the passover, which was not to be totally omitted, nor deferred any longer; and it was to be kept on the same day of the month, and at the same time of the day the first passover was observed; still the more to keep in mind the saving of their firstborn; and their deliverance out of Egypt at that time: an instance of keeping such a passover we have in ( 2 Chronicles 30:1 2 Chronicles 30:2 )

[and] eat it with unleavened bread and bitter [herbs];
in the same manner as the first passover was eaten, ( Exodus 12:8 ) ; only no mention is made of keeping the feast of unleavened bread seven days, which some think those were not obliged unto at this time, only to keep the feast of the passover.