Brachot 33 - Incidents while praying
The Standing prayer (Amidah) allows for no interruptions; even if the king were to inquire about his welfare, he should not answer. That, however, is only true of a Jewish king, who is cognizant of the law, but not answering to a non-Jewish king may be dangerous, and there one should return the greeting.
It once happened that a pious man was praying while on the road, and a Roman general greeted him, but he did not return the greeting. The general waited until he finished his prayer, and then asked, "It says in your Torah, ' watch yourself ' and ' watch your souls greatly ' By not answering you violated your own Torah and put yourself in danger. I could have cut your head off with my sword!" The pious man explained, "If you were standing in front of a king and someone greeted you, would you answer?" The general said, "No!" The pious man concluded, "How much more so for me, who was standing in front of the King of Kings!"
Even if a snake coiled around his heel, he should not interrupt his prayer. That is true, however, only of a snake that is not likely to bite. There was once a creature called "arod," a mixture of a snake and a lizard, who was hurting people. They told Rabbi Chanina ben Dosa about it, and he came and put his heel over its burrow. The arod bit Rabbi Chanina and died. At this time they said, "Woe to a man who meets an arod, but woe to an arod who meets Rabbi Chanina." Rabbi Chanina then put the dead arod on his shoulders and brought it to school, saying, "It's not the arod that kills, but it's the person's imperfections that do."
After Shabbat, one says "Blessed is the One who made a difference between Shabbat and weekday" in the blessing asking for wisdom. Wisdom is the first request in prayer, since without it nothing else is possible.
Art: Paulus Van Somer - King James I of England