The way of the just is uprightness; or, the path for the just is straight. It is one of the main blessings of the righteous that God "makes their way straight before their face" (Psalms 4:8), "leads them in a plain path" (Psalms 27:11), "shows them the way they are to walk in" (Psalms 143:8), so that they are for the most part free from doubt and perplexity as to the line of conduct which it behooves them to, pursue.
If this is so in the present life, still more will it be the uniform condition of the just in another sphere. Then God will of a surety "direct all their paths" (Proverbs 3:6). Thou, most upright, dost weigh; literally, O upright One, thou dost weigh.
The term "upright" is applied to God in Deuteronomy 32:4; Psalms 25:8; and Ps 92:16. By "weighing the path of the just" is meant keeping it, as Justice keeps her scales, straight and level.