39 Again he went away, and prayed, saying the same words.
Mark 14:39 Cross References - WEB
Matthew 6:7
7 In praying, don’t use vain repetitions, as the Gentiles do; for they think that they will be heard for their much speaking.
Matthew 26:42-44
Luke 18:1
1 He also spoke a parable to them that they must always pray, and not give up,
2 Corinthians 12:8
8 Concerning this thing, I begged the Lord three times that it might depart from me.