Is it obligatory to scrape a wall that was painted with oil, then became ritually impure (najis), and the impurity dried and was treated by painting another layer over it, in order to remove the impurity?

The religion of Allah is ease and is built upon alleviation and removing hardship. Peeling off a new layer of paint to remove impurity from underneath it involves hardship. Some scholars (the Hanafis and Ibn Taymiyyah) hold that the earth is purified by dryness, and whatever is connected to it, like trees and buildings. Even if it were said that it is obligatory to purify the earth and what is connected to it, such as a wall, even if the impurity has dried, then purification would be by increasing the amount of water without difficulty. The purification of a spot or a wall is not obligatory in itself, but rather it is obligatory for the sake of prayer. The presence of paint on the wall prevents the impurity from reaching the body or clothing of the one who touches it. If the effect of the impurity is prevented from reaching the worshipper's body or clothing, then its removal is not obligatory.