You may do the Pidyon HaBen even at the night before since it is called the thirty first day from when he was born, even though it didn’t pass a complete month.
Explanation:
The Mishna in Bechorot says that the thirtieth day from birth is considered within the thirty days and one must do the pidyon only the next day. The Gemara explains :What is the reason? We learn Chodesh Chodesh from the Pidyon in the midbar (Rashi the Pidyon in the midbar of the Bechorot were from over one month.) Over there it was more than a month so too here it is only more.
The Poskim argue how long does one need to wait from the time of birth to do the Pidyon.
Rabbeinu Gershom writes we learn from the passuk maalah, it has to be more than thirty days , that is a moon month which is 29 days , 12 hours and 793 divisions (about 44 minutes) and more, which is thirty days twelve hours and 793 divisions.
The SeferYeraim (140) writes that one needs to do Pidyon on the thirtieth day. The Passuk says to do the Pidyon “Miben Chodosh” that means thirty days one every Chodosh in the Torah is a moon month . and the month ash to be complete form the tome he was born. It is better for you to do it afterwards then before, since if y did the Pidyon after you fulfilled your obligation is not the best, but beforehand you did not. So rules the Shach in YOD 305.
The Shulchan Aruch writes : A Bechor is not eligible for a Pidyon until he passes thirty days old. After thirty-one do Pidyon immediately so the mitzvah should not wait and if the thirty first day on shabbat rather wait for Sunday.
The Shulchan Aruch says one must wait for the thirty first day but the acharonim argue if the Shulchan Aruch meant the thirty first day but after the time of birth or it doesn’t matter.
The Magen Avraham understood that when the Shulchan Aruch said you may do Pidyon on the thirty first it was to be stringent and therefore he must wait until after 29 days etc. but if thirty days didn’t ‘pass then he may not. Even if he waits until the thirty first he must pass 30 days 12 hours etc.
The Aruch Hashulchan however understood that you may do pidyon on the thirty first day what ever time.
There are four opinions:
Rabbeinu Gershom said must wait thirty days 12 hours dn 793 divisions.
The Yeraim says y only need to wait 29 days 12hours and 793 divisions, so ruled the Bach and the Shach.
The Magen Avraham wrote you need to wait whichever is later, thirty days or 29 days etc.
The Aruch Hashulchan says you need to wait thirty days and you may do pidyon at the beginning of the thirty first day and so it seems from the Shulchan Aruch .
R’ Ovadia Yosef wrote that you rely you do not have to wait until the 29 days etc. pass, however one who wants to be stringent he can.
In our situation one may do the Pidyon on Tuesday night even though the full 29 days etc. did not pass yet. Nor do you have to wait until 7:40 .
