Jesus taught on prayer. When He did, three times in three verses we find the phrase "When you pray..." (Matthew 6: 5, 6, 7, emphasis added).
After all He would do for them, it was inconceivable that they would not even talk to Him in prayer after He had gone. It is astonishing that the church in much of the world does not talk regularly.
Luther said that prayer is "the real calling of all Christians." Andrew Murray says that prayer is the "highest part of the work entrusted to us, the root and strength of all other work."