Saul's age
Whether the numbers for Saul's age and reign are corrupt, and what they once read.
1 Samuel 13:1
1Saul was thirty years old when he became king, and he reigned over Israel forty-two years.
What each tradition says
Rabbinic / Midrashic
Rashi explains that Saul was like a one-year-old who had not tasted sin. Alternatively, he reads “Saul was a year in his reign” as the first year he was made king, while noting Saul actually ruled over Yisroel two years.
Rashi (Solomon ben Isaac), Rashi on I Samuel - The Metsudah Tanach Series (Sefaria) — Comment on 1 Samuel xiii. 1
Patristic
No sourced position found. Checked Chrysostom's Homilies on the Acts of the Apostles (NPNF1-11), Augustine's City of God (NPNF1-02 - Saul appears only in the chronology of the kings), Clement of Rome and Origen (ANF vols. 1, 4) - no patristic comment on the numerals of 1 Samuel xiii. 1 found.
Catholic
Haydock explains “of one year” as meaning Saul was good and like an innocent child, and continued in that innocence for two years. He notes the verse is omitted in some copies of the Septuagint and is extremely difficult to explain; some translate the Hebrew as “Saul was a son of one year old.”
George Leo Haydock, George Haydock's Catholic Bible Commentary (1859) — Comment on 1 Samuel xiii. 1
Orthodox
No sourced position found. Checked Philaret's Longer Catechism (no treatment of Saul's reign), Chrysostom's Homilies on the Acts (NPNF1-11), John of Damascus (NPNF2-09), Cyril of Jerusalem and Gregory Nazianzen (NPNF2-07) - no Eastern statement on the numerals of 1 Samuel xiii. 1 found.
Reformed / Protestant
Gill reports that some understand the words of Saul himself, taking the number as defective and supplying thirty or forty years, or whatever age he was when he began to reign. Others take it figuratively: Saul was like a one-year-old child in purity and innocence, as the Targum says, without faults when he reigned.
John Gill, John Gill's Exposition of the Whole Bible — Exposition of 1 Samuel xiii. 1, first clause (the senses given of the words)
Evangelical
Jamieson, Fausset & Brown note that some writers regard 1 Samuel 13:1 as mutilated and defective. They cite Origen’s Hexapla, whose Greek reading gives Saul’s age and a blank for his reign; Houbigant, Wall, and others fill that blank as forty.
Jamieson, Fausset & Brown, Commentary Critical and Explanatory on the Whole Bible — Note on 1 Samuel xiii. 1 (the mutilated text and the Hexapla reading)