The first psalm at Vespers to-night was an old favourite: Psalm 138(139), Domine probasti me et cognovisti me. But what caught mine eye was its last half-verse (24b): Et deduc me in via æterna – "and lead me in the way everlasting".
“And see,” says he, “if there be any way of wickedness in me, and lead me in the way everlasting” (Ps 138:24). “Search,” he says, “my paths,” that is, my counsels and thoughts “and lead me in the way everlasting”. What else says he, but “lead me in Christ”? For who is “the way everlasting,” save He that is the life everlasting? For everlasting is He who said, “I am the Way, and the Truth, and the Life.” (St John xiv, 6) If then you find anything in my way which displeases Thine eyes, since my way is mortal, do Thou “lead me in the way everlasting,” wherein is no iniquity; for even “if any man sin, we have an Advocate with the Father, Jesus Christ the righteous; and He is the propitiation for our sins;” (I John ii,1-2) He is “the Way everlasting” without sin; He is the Life everlasting without punishment.
(St Augustine, Exposition of Psalm 138)
A check of the various versions I had to hand elucidated a few points; as in the neo-Ciceronian version of the Psalms issued under Pius XII, the last word could be rendered instead as antiqua (where the Old Roman Psalter, the Vulgate and the New Vulgate all agree instead on æterna), since apparently the Hebrew has this sense in Jeremias vi, 16. Mgr Knox followed this in his version: "and thyself lead me in the ways of old". But to pray, "Lead me along the ancient way", however sure and true that is, does seem to miss the richness of meaning inherent in "lead me along the eternal way". (One Jewish version even suggests rendering the whole phrase as "lead me in the way of the world", which seems surely a very carnal if not a well-nigh sinful interpretation!) After all, we live in the time of the New and Eternal Testament : "ancient types have long departed..."
One Bible I consulted gave some useful parallels in other psalm-verses: "Lord, lead me in Thy righteousness" (Ps 5:9(8)a); "He hath lead me in paths of righteousness for His Name's sake" (Ps 22(23):3b). Certainly the "eternal way" would be a path of righteousness, especially since Christ, the Eternal Who is the Way, is also Righteousness Incarnate.
I also found a parallel to via æterna in Tobit xii, 9, wherein almsgiving is said to effect finding mercy and "the eternal way", since it purges away sin and delivers from death. Our Lord likewise commends such...
Another favourite psalm-verse that is a clear parallel is found in Psalm 142(143):10b – Spiritus tuus bonus deducet me in terram rectam: "Thy good Spirit shall lead me into the right land". Did not the Lord give us another Advocate, the Holy Ghost, Third Person of the Trinity, Who shall lead us into all truth? Lead me, Lord, Lifegiver, Spirit of Truth!
Et deduc me in via æterna.