Many think that the posture we take in prayer is unimportant. There is a kernel of truth in this. First of all, the “inward affection” of prayer is undoubtedly most important. There is no positive command to take a certain prayer posture above another. Moreover, several different prayer postures are suggested by the saints in Scripture. This makes it both dangerous and suspect to demand any one posture be the “set prayer posture” of Christians (this includes raising one’s hands).
Still, the Scriptures at least suggest that we should, if we are able, pray on our knees on occasion. One could cite Psalm 95:6 on this point, but I think the example of holy people in Scripture is most compelling. On several occasions in the New Testament the saints pray on their knees. Jesus knelt to pray to his Heavenly Father in the Garden of Gethsemane (Luke 22:41). In Acts 9:40, Peter knelt to pray for Tabitha. Stephen prays on his knees for those executing him in Acts 7:60. Paul says that at least on occasion he interceded in prayer for the Ephesian church on his knees (Eph 3:14). This Ephesian reference is most interesting, since it is in Acts 20:36 that we are told that while saying goodbye to the Ephesian elders Paul “knelt down and prayed with them all.” I wonder if, while reading Paul’s letter to them, the Ephesian pastors remembered Paul’s kneeling in prayer with them to conclude that precious farewell.
Most importantly, we should not say that posture is unimportant during prayer. As a father, I am not particularly fond of my children slouching during prayer. Like so many parts of our habits and customs, posture communicates. The great Bible commentator John Calvin agrees. He observes from Paul’s kneeling in prayer in Acts 20:36,
The inward affection is indeed the chiefest thing in prayer; yet the external signs, as kneeling, uncovering of the head, lifting up of the hands, have a double use; the first is, that we exercise all our members to the glory and worship of God; secondly, that by this exercise our sluggishness may be awakened, as it were.
There is also a third use in solemn and public prayer, because the children of God do by this means make profession of their godliness, and one of them doth provoke another unto the reverence of God.
And, as the lifting up of the hands is a token of boldness and of an earnest desire, so, to testify our humility, we fall down upon our knees.