Quoting Commentary for I Samuel 13:8

Were for the son of Shaul Were for the son of Shaul similar to (Shmuel I, 13, 8) "until the time of Shmuel" of Shmuel.

circle them The Divine Standard of Justice said to the Omnipresent, “Lord of the universe, why did You dismiss Saul for David?” [God] replied, “Because he did not wait seven days for Samuel as he had commanded him” [as in I Sam. 13:8–14]. The Holy One, blessed be He, said [further], “Now I shall test David: Circle them.” And David observed this.

למען יאריך ימים TO THE END THAT HE MAY PROLONG HIS DAYS [IN HIS KINGDOM] — From the positive statement you may derive the negative (that if he does not fulfil the commandments his kingdom will not endure). And so, indeed, do we find in the case of Saul that Samuel said to him, (I Samuel 10:8) “Seven days shalt thou tarry, till I come unto thee” to offer burnt sacrifices, and it is written, (I Samuel 13:8) “and he tarried seven days”, but he did not keep his promise to wait the whole of the seventh day and had scarcely finished offering the burnt offering when Samuel came (I Samuel 10:10) and said to him (I Samuel 10:13-14) “Thou hast done foolishly; thou hast not kept [the commandment of the Lord thy God, which He commanded thee; for now would the Lord have established thy kingdom upon Israel forever;] but now thy kingdom shall not continue”. Thus you learn that for the neglect of an unimportant command given by means of a prophet he was severely punished.