Answered by Shaykh Amjad Rasheed
I bought a leather jacket from the market. Do I have to wash the jacket before praying in it?
In the Name of Allah, Most Merciful and Compassionate
What is explicitly stated in the books of the school is that by coming into contact with the tanning agent (which became affected by filth though the moist parts of the filthy hide [h: that it was applied onto]), tanned hide becomes like a garment affected by filth. It is therefore obligatory to wash [h: the jacket] with purifying water (Tuhfa, 1.309) and accordingly, if one does not have certainty that this jacket was washed after being tanned, it is obligatory for one to wash it if one wants to pray in it. Otherwise, one will be praying with filth.
Amjad Rasheed
Amman, Jordan
(Translated by Hamza Karamali)