What is the meaning of "Mikreh Hu"?
Rashi: He is Tamei due to a seminal emission.
Radak citing Targum Yonasan: Perhaps it occurred that he is not Tahor, or perhaps he went on the road, and we did not invite him. 1
According to the latter Perush, why was Sha'ul angry when Yehonason said that he went to his family? He was not invited to the meal! Perhaps even though he was not invited, Sha'ul considered him a rebel, and Yehonason should not have authorized him to flee. (PF)
If he is Tamei, may he not eat?
Rashi: After immersing, he is Tahor for Chulin. (They were not Kohanim, so they were eating Chulin.) He assumed that David did not immerse yet, and he did not want to be Metamei the meal. 1 Malbim - they would eat Chulin in Taharah. 2
Radak #1: Tahor people were careful not to eat with Temei'im, even for Chulin.
Radak #2: Perhaps they were eating Shelamim. The king would offer a Shelamim on Rosh Chodesh.
Radak #3: It is improper to come to the king's table when Tamei.
Why did Sha'ul attribute David's absence to Tum'ah? David fled Sha'ul, for he was trying to kill him!
Radak (2): After David fled from Nayos, Yehonason returned him to Sha'ul's table like he used to [eat there every day]. Even so, David was afraid, and wanted to test Sha'ul's reaction when David is absent, to see if Sha'ul's servants were correct [that Sha'ul wants to kill him even not at the time of Ru'ach Ra].
Malbim citing Mahari: Amidst hatred of David, he said that because he is not Tahor and thinks [about women] during the day, he comes to Tum'ah at night. 1
If not for hatred, he would have judged him favorably, e.g. David was Tamei due to relations with his wife, e.g. she immersed from Tum'ah the night before. However, perhaps also she used to eat in her father's house, and through this Sha'ul knew that this was not the case. (PF)
