Blessed are the undefiled in the way - In the way or journey of life; in the path of religion; in the road which leads to heaven. As life - the religious life - is represented under the image of a journey, the expression here is equivalent to saying, “Blessed are those who in the journey of life - in their religious course - are pure, Sincere, uncontaminated.” On the word way, see the notes at Psalms 1:6. The margin here on the word undefiled, is perfect, or sincere. So the Hebrew. The word is the same as in Job 1:1, where it is rendered “perfect.” See the notes at that passage. The Greek translation is undefiled - ἄμωμοι amōmoi. So the Latin, “immaculati.” Luther renders it, “Who live without blemish” or stain. The idea is, “Blessed are they who are upright, sincere, perfect, in their course.” The whole psalm is designed to illustrate this thought, by showing what the influence of a sincere and conscientious attachment to the principles of the law or word of God in the various circumstances of life must be.
Who walk in the law of the Lord - Who habitually obey his law. This constitutes sincerity, uprightness, perfection in a man’s life, for the law of the Lord is the only just rule of human conduct.