In India, there is a tradition to dress baby in old clothes during the first few days/weeks. Usually, clothes of an older sibling or a cousin are handed down for this purpose.
In fact, many people consider it inauspicious to do any shopping for the baby before the baby is born. This belief stems from the fact that these old used clothes are soft and less likely to cause any sort of irritation or allergy to newborn baby’s delicate skin.
In current times, with more and more nuclear families, it is not always possible to get old clothing. So, most parents buy new clothes and wash it a couple of times to ensure clothes are not new and fabric is softer on baby’s skin.