פירוש על שמואל א 27:7

Days and four months. The minimum [number] of days is two. It is impossible to explain this word, 'יָמִים' as a year³As we find יָמִים to mean ‘year’ in Bereishis 41:1. because Dovid did not go to Achish until Shmuel had died, and Shaul only reigned after Shmuel's death⁴Therefore יָמִים is to be taken literally, i.e., days. four months, as we learned in Seder Olam. Also [this can be deduced from the following:] the number of Eili's years [forty years which he judged Yisroel],⁵Above 4:18. and the twenty years that the Ark was in Kiryas Ye'arim⁶Above 7:2. total sixty years. Subtract from that Shmuel's fifty-two years, plus one year from his conception, with these four months, plus the seven years which Dovid reigned in Chevron⁷II Shmuel 2:5. before he brought the Ark from Kiryas Ye'arim. This [calculation] discloses that Shaul reigned after Shmuel's death but four months.