And the explanation of the evidence that saliva is not impure. Because if it were impure and unclean, the Prophet (peace be upon him) would not have ordered the one praying to spit it into his garment during prayer.

It is narrated from Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) liked very much to hold a bunch of dates in his hand. One day, he (peace and blessings be upon him) entered the mosque while he had a bunch in his blessed hand. He (peace and blessings be upon him) saw phlegm on the qiblah side of the mosque, so he scraped it off and cleaned it thoroughly. Then, in a state of severe displeasure, he (peace and blessings be upon him) turned towards the people and said: "Would any of you like that someone comes and spits on his face? Surely, when any one of you stands for prayer, he stands facing his Lord, and an angel is on his right side. Therefore, he should not spit in front of him nor on his right side; he should spit under his left foot or on his left side. But if he is in a hurry, he should spit into a corner of his garment and then fold that corner together." Janab Duraqi says that our respected teacher Janab Yahya demonstrated this to us in this manner.