Sayings Comparing the Wise and the Unlearned and Thoughtless (Ecclesiastes 10:1-3).
‘Dead flies cause the ointment of the perfumer to smell and putrefy, so does a little folly outweigh wisdom and honour.'
The effect of dead flies in ointment is to ruin the ointment which had previously been so sweet smelling. In the same way the effect of folly, either his own or another's, can destroy all of a man's wisdom and reputation, because one example of such folly may counterbalance all he is and has done, like the fly in the ointment. It may destroy his reputation. It may cause annoyance and result in antagonism or lack of confidence, and thus prevent co-operation. Or it may ruin whatever wisdom has been presented by others. There are some things that are never forgotten, so we should be careful what we say. One piece of folly can counteract a great deal of wisdom.
‘A wise man's heart is at his right hand, but an unlearned man's is at his left.'
The right side is the side of the sword arm and the right arm is the strongest, at least in theory (compare Psalms 16:8; Psalms 110:5; Psalms 121:5) Thus the heart at the right side is better protected. The point is that the wise man protects what is most important, and allocates his strength accordingly (compare Ecclesiastes 2:14). Also it could indicate that the wise man ensures that he uses his strength properly in order to protect what he deems is most important. His thinking means that he makes use of his stronger capacity when it is really needed. The unwise may be more careless.
‘Yes also when the fool walks by the way his understanding fails him, and he says to everyone that he is a fool.'
The point here is that a man soon reveals by his actions whether he is sensible or thoughtless in whatever he is doing. The wise man used his right hand to protect himself and his wisdom. The fool soon gives himself away. He goes out without protection. The illustration probably has in mind the need in those days to ensure readiness for trouble when using a byway. The unwise are careless and slack and are not on the alert. They travel without their weapons. Thus all know they are fools. They are unprepared.