Luke 18:1

And he spoke a parable to them to show that they ought to pray always, and not be fainthearted:

Philippians 4:6

Be anxious about nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God;

Colossians 4:2

Persevere in prayer, being watchful therein with thanksgiving;

Treasury of Scripture Knowledge

Summary

Because he hath inclined his ear unto me, therefore will I call upon him as long as I live.

Bible References

Therefore

Luke 18:1
And he spoke a parable to them to show that they ought to pray always, and not be fainthearted:
Philippians 4:6
Be anxious about nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God;
Colossians 4:2
Persevere in prayer, being watchful therein with thanksgiving;