Contradiction with Matthew 6:7
This verse advises against vain repetitions in prayer, whereas Ephesians 6:18 encourages praying always with all perseverance.
Matthew 6:7: But when ye pray, use not vain repetitions, as the heathen [do]: for they think that they shall be heard for their much speaking.
Contradiction with Ecclesiastes 3:1
This verse mentions a time for every purpose, which may contradict the notion of praying always as mentioned in Ephesians 6:18.
Ecclesiastes 3:1: To every [thing there is] a season, and a time to every purpose under the heaven:
Contradiction with Luke 12:30
Here, the emphasis is on God knowing our needs and providing for them, potentially contradicting the need for continual prayer expressed in Ephesians 6:18.
Luke 12:30: For all these things do the nations of the world seek after: and your Father knoweth that ye have need of these things.
Contradiction with Matthew 6:8
This verse suggests that God knows what you need before you ask, which might contradict the need for persistence in prayer noted in Ephesians 6:18.
Matthew 6:8: Be not ye therefore like unto them: for your Father knoweth what things ye have need of, before ye ask him.
Contradiction with 1 Thessalonians 5:17
While this verse also emphasizes continual prayer, it conflicts in the sense that it simplifies the act to "pray without ceasing" without the added instruction of being watchful and perseverant as in Ephesians 6:18.
1 Thessalonians 5:17: Pray without ceasing.