1 Samuel 1:12
Hannah prayed to Jehovah for a long time. Eli watched her lips.
Luke 11:8-10
I tell you even if he will not rise and give you what you need because he is your friend, he will arise and give you what you need because you keep asking.
Luke 18:1
He spoke an illustration to them emphasizing the need to pray and not become tired:
Ephesians 6:18
With prayer and supplication pray at all times in the Spirit. Watch with all perseverance and supplication for all the holy ones.
Colossians 4:2
Continue steadfastly in prayer, being vigilant with thanksgiving.
1 Thessalonians 5:17
Pray without ceasing.
James 5:16
Confess therefore your sins one to another, and pray one for another, that you may be healed. The prayer of a righteous man helps much.