Commentaire de citation sur Samuel 1 7:9

עבודת מתנה אתן את כהונתכם, “I make your priesthood a service of dedication.” The performance of the sacrificial duties which I (G’d) impose on the priests are not to be viewed as menial tasks but as a major service and a gift from Me to you. Apart from the fact that you derive your livelihood from the performance of these duties you are to consider it as an honor and glory bestowed upon you.
The reason that the Torah repeats here once more that “the stranger who approaches (unauthorized) shall die,” is because this time it is not addressed to members of other tribes but to priests who for one reason or another have become disqualified. Even Levites are subject to this warning. If we find that the prophet Samuel (a Levite, not a priest) offered a burnt-offering (Samuel I 7,9) this was an exception dictated by special circumstances. It was similar to Gideon (a member of the tribe of Menashe) who is also reported as offering a sacrifice (Judges 6,25-27). Moreover, seeing that this paragraph deals with the situation in the desert and the period when the Tabernacle had recently been erected and the firstborn had been replaced by the Levites, there is ample reason to repeat the warning once more. (Rabbi Chavell points out that the sacrifice offered by Samuel on a private altar after the destruction of he Tabernacle in Shiloh was perfectly permissible for any Israelite and that there is nothing strange about what Samuel did there although he was the first one to do so. Compare Avodah Zarah 24.
According to the Talmud Temurah 28 the night on which Gideon offered a sacrifice was historically important as no fewer than eight prohibitions were waived on that night).

והזר הקרב, “and a non priest or Levite who dared to approach into the sacred domain, etc.” The Torah speaks of such a stranger presuming to perform service within the Temple. Such a stranger would also be punished, even if he had been ritually pure. Even a Levite, if he had presumed to perform Temple service would be subject to the death penalty. If you were to ask that we know that Samuel the Levite is reported to have offered sacrifice on the altar (Samuel I 7,9), this was due to an emergency, just as Gideon offered a sacrifice (Judges 6.26).

To cause you to cross over in the covenant All of you are ready to cross into the covenant, and all of you are together. And for this it's good to execute the commandment now, that not one of you is able to say: I was not in the covenant, and did not accept the covenant upon myself. Since when you will cross the Yarden and be scattered each man to his inheritance and portion, it will be impossible to gather all of you together as you are now - since it's impossible that there will be no birthing woman or sick person or person kept aaginst their will, or lame person, and it's impossible to leave the houses and cities without any creature. But now, behold all of you are in one area and one camp, and all of you hear and see the execution of the covenant, and not one of you is able to withdraw and say 'I was not in the covenant'. "Execution [lit. "cutting" כריתות] of the covenenant" since they cut the calf into two, and "to cause you to cross over" since they passed between the parts of the calf that Avraham our father did between the parts, as it says "and divided them in the midst" (Bereishit 15:10). And like they did when they executed the covenant to send the slaves free (Yirmiyahu 34:13), the calf which was cut into two and they passed between the parts, this is a sign that when you pass over the covenant this is how it will be cut. Like, "And Shmuel took one milk-goat" (I Samuel 7:9), "And Tzamad took a cow and cut it into parts" (I Samuel 11:7) -- to say, which will not go after Shaul and after Shmuel, so will be done to his cow.