John Calvin on Acts 20:36

36. And kneeling down. 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 “Fiduciae,” confidence. and of an earnest desire, so, to testify our humility, we fall down upon our knees. But he sealeth up and concludeth that sermon which he made before with prayer; because we can hope for no profit of our doctrine, save only from the blessing of God. Wherefore, if we be desirous to do any good by teaching, admonishing, and exhorting, let us always end after this sort; to wit, with prayer.