Jesus taught that prayer must be with persistence—not losing heart (from Matthew 7:7-8, Luke 11:5-10, and Luke 18:1-8)

Jesus taught this lesson of persistence in prayer from two different stories, on two different occasions.  One of His stories, recorded in Luke 11:5-10, is about a man who needed bread and who goes to his friend at midnight and begs for it until his friend gives him the bread.  The other story, in Luke 18:1-18, similarly, is about a widow who goes before an unjust judge and pleads for justice from her adversary; and she continues to come to him, begging for justice, until he finally gives it to her.   

We will not go into all the details of the stories (you can read the stories yourself).  However, I want to emphasize the central teaching: that when we pray we must pray with persistence and not lose heart