When Rosh Chodesh falls on Sunday, the Shabbes before we swap the normal shabbes haftara for a haftara called ‘machar chodesh,’ in sefer Shmuel. However, upon first glance, the only thing that the entire haftara has to do with rosh chodesh are the two words ‘machar chodesh’ (tommorrow is rosh chodesh). Did Chazal make us do away with the normal haftara for just 2 word of relevence? Rav Shwab answers that there is a deeper connection to Rosh Chodesh. In this haftara, Shaul asks ‘why has Ben Yishai [referring to David] not come [to attend my meal].’ And the answer is that David was hiding from Shaul’s baseless hatrid of David [caused by this ruach ra’ah on Shaul]. On Rosh Chodesh mussaf we speak of the Beis Hamikdash offerings, and thus, says Rav Shwab, this haftara reminds us why we do not have the beis hamikdash today. Why has ‘ben yishai [ie the Moshiach] not come?’ Because of baseless hatred. That’s the lesson of this carefully selected haftara.