Luke 11:8-10
"I tell you that even if he will not rise and give him the loaves because he is his friend, at any rate because of his persistency he will rouse himself and give him as many as he requires.
Luke 18:1
He also taught them by a parable that they must always pray and never lose heart.
Ephesians 6:18
Pray with unceasing prayer and entreaty on every fitting occasion in the Spirit, and be always on the alert to seize opportunities for doing so, with unwearied persistence and entreaty on behalf of all God's people,
Colossians 4:2
Be earnest and unwearied in prayer, being on the alert in it and in your giving of thanks.
1 Thessalonians 5:17
Be unceasing in prayer.
James 5:16
Therefore confess your sins to one another, and pray for one another, so that you may be cured. The heartfelt supplication of a righteous man exerts a mighty influence.