To set the mind on the flesh means to exercise the mind to consider the things of the flesh.
For example, to set your mind on worldly fashions or advertisements in the newspaper is to set it on things of the flesh.
Likewise, to consider the weaknesses of your wife or husband is to set the mind on the flesh. The result of this is death.
Darkness, Uneasiness And Unrest
The death caused by setting the mind on the flesh is not, of course, the kind of death that causes you to die physically and be buried in the grave.
No, this death has other symptoms, such as darkness and uneasiness. When you feel uneasiness and unrest within, that is a sign of death.
Dissatisfaction is another symptom. Perhaps in your time with the Lord in the morning you are very satisfied with the Lord, but after breakfast you set your mind on the advertisements in the newspaper.
The more you consider them, the more dissatisfaction you are conscious of within.
This dissatisfaction is a sign of death.
Weakness is another sign. As we all know, the ultimate point of weakness is death.
When someone is weak to the extent that he can no longer breathe, he dies. That is the consummation of weakness. Hence, weakness is an expression of death.
Another sign of death is dryness. When you feel dry within, with no sense of being watered, you are in death.
Those In The Spirit Will Be Able To Sense It
All these items—darkness, uneasiness, dissatisfaction, weakness, and dryness—are signs of inward spiritual death.
Whenever you set your mind upon fleshly things, you will be conscious of one or more of these signs of death. To be filled with such things is to be filled with death.
Whenever you are suffering from inward death, those in the spirit will be able to sense it. They will realize immediately that you are filled with death.
Your prayers indicate this. You may pray, but there will be no life in your prayers; instead, there will be death. Instead of watering, there will be dryness.