There are several explanations for the custom of sholom zochor:
• At the sholom zochor we offer thanks to G-d that the baby was born safe and sound.
• Talmudic literature tells us (Niddah 30b) that in the mother’s womb, a baby is taught the whole of Torah. As he is born he forgets all that he has learnt. Another explanation for the Sholom Zochor is connected to this – we come to console the child who has just forgotten all the Torah.
• According to kabbalah, a child is not ready to be circumcised until he has experienced a Shabbat. Judaism believes that Shabbat provides the infant with the spiritual power necessary to enter into a lasting covenant with God. This is one of the reasons why the brit is on the eight day, to ensure that a Shabbat passes. For this reason we make a special celebration on the Shabbat after the baby is born.
There is a custom to serve chickpeas or lentils at a Sholom Zochor, as they are round food and represent the cycle of life.