Friday in the 6th Week of Easter: 1st Day of the Pentecost Novena
…for every novena of preparation, as also for every novena of prayer, not only the best explanation but also the best model and example was given by Christ Himself to the Church in the first Pentecost novena. He Himself expressly exhorted the Apostles to make this preparation. And when the young Church had faithfully persevered for nine full days in it, the Holy Ghost came as the precious fruit of this first Christian novena for the feast of the establishment and foundation of the Church.
—Catholic Encyclopedia: Novena
All these were persevering with one mind in prayer…