وَإِنْ أَصَابَتِ الْأَرْضَ نَجَاسَةٌ فَجَفَّتْ بِالشَّمْسِ وَذَهَبَ أَثَرُهَا: جَازَتِ الصَّلَاةُ عَلَى مَكَانِهَا، وَلَا يَجُوزُ التَّيَمُّمُ مِنْهَا.
Translation: If filth reaches the earth, then dries by the sun and its trace disappears, prayer there is permissible, but tayammum from that earth is not permissible.
Two separate rulings appear here: fitness of the prayer location and fitness of the soil for tayammum. Removal of the visible trace allows prayer at the spot under this ruling, but tayammum requires the separate condition of purified earth.