´It was narrated from Sa'eed bin Al-Musayyib that:` He disliked putting the dregs of Nabidh into (new) Nabidh lest it become strong because of the dregs.
Explanation & Benefits
Hafiz Muhammad Ameen
The details of this matter have already been explained in Hadith 5743, that some people would filter the nabidh from the top and leave the sediment remaining at the bottom as it was. They would then pour new nabidh over it from above. The purpose of this was to increase the sharpness (intensity) of the nabidh. It is evident that there is a possibility of intoxication in the old sediment; therefore, this method is incorrect. It is against the objectives of the Shari‘ah, especially when this act is repeated multiple times.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 5747