Can what is stated in "Al-Fatawa al-Hindiyya" – that a garment does not become impure if it passes over wet impure ground and has not reached the extent that if it were squeezed, something would flow from it – be relied upon for praying in outdoor clothes that have come into contact with sewage water?

Islamic law is founded on ease and the removal of hardship. Among the principles of jurisprudence are that difficulty brings ease, and that when a matter becomes restricted, it expands. Examples of this include pardoning street mud, even with the possibility of its impurity, and even pardoning a small amount of certain impurity, due to widespread affliction and the difficulty of avoiding it.

The Shafi’is and Hanbalis have explicitly stated that a small amount of certain impure mud is pardoned. If impurity is certain and you did not pass through a pure path, then this is pardoned if it is a small amount, and impurity should be avoided as much as possible.

If a pure garment comes into contact with an impure garment or impure ground, and one of them is wet, then impurity transfers to the pure one according to the Shafi’is and Hanbalis, and mere wetness or dampness is sufficient.