Is a traveler's prayer valid if his clothes have been contaminated by the saliva of a dog that bit him, and what are the implications of that thereafter?

The relied-upon opinion is that a dog's saliva is impure (najis), and whatever it touches on the body or clothes must be purified by washing it seven times, one of which is with earth or what serves its purpose, like soap. Purification is only required for what is certainly known to have been touched by the impurity. One who prays having forgotten about the dog's impurity, their prayer is valid and does not need to be repeated. However, one who prays knowingly and intentionally, they must repeat it. As for one who prays while ignorant of the ruling, the majority of scholars hold that repetition is obligatory, and this is more cautious.