Luke 11

We commonly quote the words of the Savior -

"...I say unto you, Ask, and it shall be given you; seek, and ye shall find; knock, and it shall be opened unto you.
10 For every one that asketh receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened."  (New Testament | Luke 11:9 - 10)

But many times we do not consider the parable that preceeded these words, that is where the Savior -

"...said unto them, Which of you shall have a friend, and shall go unto him at midnight, and say unto him, Friend, lend me three loaves;
6 For a friend of mine in his journey is come to me, and I have nothing to set before him?
7 And he from within shall answer and say, Trouble me not: the door is now shut, and my children are with me in bed; I cannot rise and give thee.
8 I say unto you, Though he will not rise and give him, because he is his friend, yet because of his importunity he will rise and give him as many as he needeth."  (New Testament | Luke 11:5 - 8)

"Importunity" would suggest persistent requests in our prayers, suggesting as the parable states, that we don't ask just once and we receive, but in many ways we must continue to ask and plead for a period before we may receive.