From Today's daf Berachot 24b:
‘One who says the Tefillah so that it can be heard is of the small of faith (as if God couldn't hear a prayer recited quietly- Rashi, also cf 31a); he who raises his voice in praying is of the false prophets (like the prophets of Ba'al who called out loudly on Mt. Carmel in the showdown with ELijah); he who belches and yawns is of the arrogant; if he sneezes during his prayer it is a bad sign for him — some say, it shows that he is a low fellow (as Rashi explains this is someone who deliberately sneezes - this also applies to belching and yawning, that it's deliberate); one who spits during his prayer is like one who spits before a king’. Now in regard to belching and yawning there is no difficulty; in the one case it was involuntary, in the other case deliberate. But the sneezing in Rabbi's case does seem to contradict the sneezing in the other? — There is no contradiction between sneezing and sneezing either; in the one case it is above (that is, the nose), in the other below (er, from a smellier bit of anatomy...)
For R. Zera said: This dictum was casually imparted to me in the school of R. Hamnuna, and it is worth all the rest of my learning (rashi: because it praises sneezers, and I sneeze a lot): If one sneezes in his prayer it is a good sign for him, that as they give him relief below [on earth](Rashi: sneezes offer nachat ruach - satisfaction or ease- to a person) so they give him relief above [in heaven].
But there is surely a contradiction between the spitting in the one case and the other? — There is no contradiction between the two cases of spitting either, since it can be done as suggested by Rab Judah. For Rab Judah said: If a man is standing saying the Tefillah, and spittle collects in his mouth, he covers it up in his robe, or, if it is a fine robe, in his turban. Rabina was once standing behind R. Ashi and he wanted to spit, so he spat out behind him. Said R. Ashi to him: Does not the Master accept the dictum of Rab Judah, that he covers it up in his turban? He replied: I am rather squeamish.
... R. Abba kept away from Rab Judah because he wanted to go up to Eretz Israel; for Rab Judah said, Whoever goes up from Babylon to Eretz Israel transgresses a positive precept, since it says, They shall be carried to Babylon and there shall they be, until the day that I remember them, saith the Lord. He said: I will go and listen to what he is saying from outside the Academy. So he went and found the Tanna10 reciting in the presence of Rab Judah: If a man was standing saying the Tefillah and he broke wind, he waits until the odour passes off and begins praying again. Some say: If he was standing saying the Tefillah and he wanted to break wind, he steps back four cubits and breaks wind and waits till the wind passes off and resumes his prayer, saying, Sovereign of the Universe, Thou hast formed us with various hollows and various vents. It is revealed and known before You our shame and humiliation in our lives, and that our latter end is worms and maggots!
Then he begins again from the place where he stopped. He said: Had I come only to hear this, it would have been worth my while.