What is the ruling on a meal prepared for postpartum women and visitors as a custom, and how do we distinguish between permissible customs and bid‘ah (innovation)?

The difference between permissible customs and innovation (bid'ah) is that innovation is intended as a means of drawing closer to Allah, whereas customs are not. The default rule for customs is permissibility, and it is not permissible to prohibit anything from them except with evidence. Worship (ibadah) is what Allah and His Messenger have commanded as a means of drawing closer to Him and seeking His reward, while custom (adah) is what people are accustomed to in their food, drink, dwellings, and clothing. The default rule for acts of worship is prohibition until evidence is established, whereas for customs, the default rule is permissibility unless evidence prohibits them. Religiously, innovation (bid'ah) is defined as worshipping Allah in a manner He has not legislated. As for ordinary matters that follow custom and tradition, these are not called innovation in religion. Acts of worship are not established except by religious law, whereas the default rule for customs is non-prohibition, unless Allah has prohibited them. Thus, customs are permissible unless they include a prohibited element such as extravagance or squandering.