Luke 18:1

And he spake a parable unto them to this end, that men ought always to pray, and not to faint;
— Luke 18:1, King James Version

In other translations

World English Bible (WEB)

He also spoke a parable to them that they must always pray, and not give up,

American Standard Version (ASV)

And he spake a parable unto them to the end that they ought always to pray, and not to faint;

Young's Literal Translation (YLT)

And he spake also a simile to them, that it behoveth <FI>us<Fi> always to pray, and not to faint,