'Steadfastly' in the Bible

All these with one mind and one purpose were continually devoting themselves to prayer, [waiting together] along with the women, and Mary the mother of Jesus, and with His brothers.

They were continually and faithfully devoting themselves to the instruction of the apostles, and to fellowship, to eating meals together and to prayers.

But we will [continue to] devote ourselves [steadfastly] to prayer and to the ministry of the word.”