So shall they fear the name of the LORD from the west,
and his glory from the rising of the sun. When the enemy
shall come in like a flood, the Spirit of the LORD
shall lift up a standard against him.
Isaiah 59:19


When it Rains It Pours 
If you take the time to look closely these words can be found on a box of Morton Salt. You will find the word 'it' two times in the sentence.  No differentiating is made between the 'its'.  However, a look at the picture explains that the two 'its" are very different. The little girl with the umbrella is in the pouring rain with a box of salt  (Morton Salt) under her arm which unbeknownst to her is pouring as she happily strolls along.  It #1 - Pouring Rain.  It # 2 - Pouring Salt.
Morton Salt was not the first to come up with the catchphrase about raining and pouring.  It originated as an old English proverb and The English Usage Dictionary describes this phrase as an idiom meaning when things go wrong, a lot of things go wrong at the same time. 
We often use the phrase in our daily lives.  But unlike the salt company ad, we use 'it' to mean the same thing.
When bad things come a lot of bad things come.  When trouble comes a lot of trouble comes.  The phrase always seems to have a negative connotation.  I don't believe I have ever heard anyone use the idiom referring to something good.
When good things come a lot of good things come.  No, I haven't heard it used in that way. Morton Salt shook things up a bit and made 'it' mean two different things... when the rain pours the salt pours.  Ah, happiness, no clogged up salt shaker on rainy days. So, I suppose Morton Salt turned the negative to positive didn't they?
Isaiah  59:19 speaks of a bad thing coming, a negative thing coming in like a flood... the enemy.  When the enemy comes into our lives seeking to steal, kill, and destroy,  it does seem like 'it' is pouring.  Satan uses so many tactics to try to defeat us.  He uses disease, debt, depression, death, disdain, discord, disaster, devastation, divorce, and all kind of devilment to discourage us. All these things pour in at once leaving us drowning in a sea of discouragement. 
BUT thank God, when 'it' (satan) rains all these things into our lives, 'IT' (our great God) reigns and raises up a standard against him. When it rains IT pours.  #1 it - satan  #2 IT - God Yes, when it attempts to rain curses, IT pours His blessings upon us. The enemy is defeated!  God turns negatives to positives every single day, rain or shine.
-The Spirit of the Lord shall put the enemy to flight; the Spirit of the Lord shall lift up a standard against him;
Christ and his Gospel, or Christ the standard lifted up in the ministry of the Gospel, a set of ministers shall be raised up, having the everlasting Gospel, which they shall publish to all nations, and which shall have a universal spread; and by means of which the earth shall be filled with the knowledge of the Lord as the waters cover the sea; and which will be a sufficient check to the enemy's flood of immorality, error, and persecution; and which, after this, shall be no more.
~John Gill