Thy testimonies are very sure - All that thou hast borne witness to; all that thou hast affirmed or declared to be true. This would embrace “all that” God has spoken, whether his law, his promises, his commands, his prophecies, or his statements of what has occurred and of what will occur. See the notes at Psalms 19:7.
Holiness becometh thine house, O Lord - The psalm seems to have been intended to be used in the sanctuary, as a part of public worship, and the word “holiness” here would seem to mean a proper respect for God; confidence in him; a state of mind free from all doubt, and from all that is impure. Perhaps there may be here, also, the idea that in all the convulsions of the world; in all that threatens to overthrow truth and righteousness; in all the attacks which are made on the divine government; in all the efforts of the defenders of error, and in the midst of abounding iniquity, the church should maintain a firm adherence to the principles of “holiness,” to that which is right and true. There should be one place - the church - where there would be no wavering in regard to truth and holiness; one place, where the truth would be defended whatever commotions might be abroad. The main idea, therefore, in the psalm is, that, in view of the fact that God reigns, and that nothing can frustrate his plans, or disturb his throne, we should approach him with reverence, with humble trust, with sincere and pure hearts.
In a larger sense, also, in the largest sense conceivable - it is true that “holiness,” purity, freedom from evil thoughts, from a wanton eye and a wanton imagination, from unholy plans and purposes, should prevail in the house of God, and should be regarded as indispensable to proper worship. As heaven is pure, and as there shall enter there nothing “that defileth, neither whatsoever worketh abomination or maketh a lie” Revelation 21:27, so in the place where we seek to prepare for that holy world - the sanctuary of God - nothing should be allowed to enter that is impure and polluting; nothing that tends to corrupt or defile the soul. It may be added, that attendance in a place of public worship is calculated to make the heart pure, and to banish unholy thoughts and purposes from the soul. A man who feels that he is in the presence of a holy God, will not be likely to welcome into his soul polluted images and unholy desires.
Forever - Margin, as in Hebrew, “to length of days.” The idea is, that it is always appropriate. See the notes at Psalms 23:6.