Pray without ceasing. Not that saints should be always on their knees, or ever lifting up their hands, and vocally calling upon God; this is not required of them, and would clash with, and break in upon other parts of religious worship, and the duties of civil life, which are to be attended to, as well as this, and besides would be impracticable; for however willing a spiritual man might be to be engaged in this work always, yet the flesh is weak, and would not be able to bear it; and it requires food and drink, sleep and rest, for its refreshment and support; for all which there must be time allowed, as well as for other actions of animal life, and the business of a man's calling.
But the meaning is, that believers should be daily, and often found in the performance of this duty; for as their wants daily return upon them, and they are called to fresh service, and further trials and exercises, they have need of more grace, strength, and assistance, and therefore should daily pray for it; and besides certain times both in the closet, and in the family, in which they should attend the throne of grace, there is such a thing as mental prayer, praying in the heart, private ejaculations of the soul, which may be sent up to heaven, while a man is engaged in the affairs of life.
The Ethiopic version renders the words, "pray frequently"; do not leave off praying, or cease from it through the prevalence of sin, the temptations of Satan, or through discouragement, because an answer is not immediately had, or through carelessness and negligence, but continue in it, and be often at it; see Lu 18:1.