The Rama writes that there is a minhag to make a seuda and festivities on the Friday night after a baby boy is born, and it has the status of a seudas mitzvah. The source is the Terumas Hadeshen, who proves that a shalom zachor is a seudas mitzvah, from the Gemara which relates that Rav and Shmuel came to a “Yeshua haben.” Tosfos explains that it was a seuda celebrating the healthy birth of a baby boy. Since the Gemara tells us that Rav would only participate in a meal which was a seudas mitzvah, we can infer that a shalom zachor is considered a seudas mitzvah. The Pischei Teshuva writes the same, in regards to someone who made a neder to only participate in a meal which is a seudas mitzvah, that he is allowed to go to a shalom zachor.
REASONS FOR A SHALOM ZACHOR
The Terumas Hadeshen based on Tosfos explains that it is a seudas hodahah of sorts, thanking Hashem for a safe delivery of the child.
The Ta z quotes a Midrash that compares a bris milah to bringing the child on the altar, and the child must first experience a Shabbos, before being fit to be brought before the King. We therefore celebrate that the baby is now ready and fit for the bris.
The Ta z also quotes the Drisha who says that this is to comfort the newborn baby who learned the whole Torah from an angel and forgot it all on his way into this world.
Another idea is brought by the Yaavetz, based on a different concept mentioned in the Gemara: “Shavua habin.” He explains that it is an expression of taking an oath, a reference to the fact that, prior to birth, every soul is told to swear that he will keep the Torah in this world. We make the shalom zachor to remind the baby of this commitment.
REASONS FOR MAKING A SHALOM ZACHOR ON FRIDAY NIGHT
The Terumas Hadeshen writes that a shalom zachor was instituted on Friday night, because that is when people are home.
According to the Ta z – that the reason for the celebration of the shalom zachor is because the child must first experience a Shabbos before the bris can take place – we celebrate on Shabbos, since the baby is now ready and fit for the bris.
The Yaavetz explains the reason for a shalom zachor taking place on Shabbos based on the other reason the Ta z gives for a shalom zachor. We comfort the newborn baby who learned the whole Torah from an angel and forgot it all on the way into this world.
This consolation takes place on Shabbos, a day of zechira – remembering, as we say in kiddush: “Remember the day of Shabbos.” The Imrei Emes adds, based on the words of the Sfas Emes, that there is a special segula to learn on Shabbos which will help a person remember what he learned. This is why we comfort him on Shabbos – a day of remembering, to give a comforting message that there is a way to learn in this world and retain what was learned.
The Shem M’Shmuel adds that we are showing the baby comfort on Shabbos Kodesh, sharing with him that there is a day that one can reach great levels of spiritual pleasure, and it was worth coming to this world.
WHEN SHOULD THE SHALOM ZACHOR TAKE PLACE IF THE BABY IS BORN ON FRIDAY NIGHT?
If the baby was born on Friday night, when there is still time to make a shalom zachor, when should it be celebrated? Should it take place that night, or should it be pushed off until the following Friday night? The Pri Megadim discusses this very question and rules that it should be on the first Friday night. As the Trumas Hadeshen explains, the shalom zachor is a seudas hodahah, thanking Hashem for the healthy birth. If so, it would be appropriate to do so right away, without delay.
The prevalent minhag, however, is to make the shalom zachor on the 2nd Shabbos.
SUMMARY
A shalom zachor on Friday night is considered a seudas mitzvah: thanking Hashem for the safe delivery of the child, celebrating that the baby is now fit for the bris, comforting the newborn baby who learned the whole Torah from an angel and forgot it all, and reminding the baby of his commitment to keep the Torah in this world.
Rabbi Scheiner
