Is it obligatory to drink the leftover ablution water, and what is the ruling on drinking it if drops from the nose or mouth fell into it, and does it remain pure for drinking in this case?

The water remaining from ablution (wudu') is pure, and scholars have unanimously agreed upon its purity. It was narrated from Ali (may Allah be pleased with him) that the Prophet (peace be upon him) drank from the remaining water of his ablution while standing. What is meant by the remaining water of ablution is the water left in the vessel or the water that falls from the limbs. It is commendable, according to the Hanafis and Shafi'is, to drink from the remaining water of ablution after finishing it, while facing the Qibla. However, this commendation is not supported by strong evidence, and it appears that the Prophet's action (peace be upon him) was to show the permissibility of drinking while standing. Therefore, drinking from the remaining water of ablution is permissible, there is no harm in it, and there is no evidence for its commendability.