1 Chronicles 10:13
12 all the warriors went and recovered the bodies of Saul and his sons and brought them to Jabesh. They buried their remains under the oak tree in Jabesh and fasted for seven days. 13 So Saul died because he was unfaithful to the Lord and did not obey the Lord’s instructions; he even tried to conjure up underworld spirits. 14 He did not seek the Lord’s guidance, so the Lord killed him and transferred the kingdom to David son of Jesse.
LXX 1 Chronicles 10:13
12 And all the mighty men rose up from Galaad, and they took the body of Saul, and the bodies of his sons, and brought them to Jabis, and buried their bones under the oak in Jabis, and fasted seven days. 13 And Saoul died in his acts of lawlessness, which he had done lawlessly against the Lord, according to the Lord’s word, since he had not kept it, because Saoul had made inquiries at the ventriloquist to find out, and the prophet Samouel had answered him. 14And he did not seek the Lord, and he killed him and transferred the kingdom to Dauid son of Iessai.
Notes and References
"... we would like to look at one instance of change in noun number. It is clear the translator is generally consistent in this regard. That makes the change in 10:13 stand out all the more. Here the narrator interprets the reason for Saul's death ... Note that the object of the preposition is in the singular. The Hebrew writer goes on to identify the single event which he had in mind. The Greek translator presents the phrase in this way ... Here the object of the prepositional phrase is plural. The implication is that the unfaithfulness of Saul is not tied to a singular event but to a stream of unfaithfulness which characterized his life. In the expansion, the incident at Endor is mentioned as an illustration of a larger pattern of life ..."
Beck, John A. Translators as Storytellers: A Study in Septuagint Translation Technique (p. 49) Peter Lang Publishing, 2000