The interpretation timeline
1 Samuel 26:8 Douay-Rheims

And Abisai said to David: God hath shut up thy enemy this day into thy hands: now then I will run him through with my spear even to the earth at once, and there shall be no need of a second time.

A.D. 258 – 1871 6 witnesses

Patristic

before A.D. 750
258
A.D.
Cyprian Patristic
c. A.D. 200–258
“But what great and wonderful and Christian patience is to be found in David from whom Christ descended according to the flesh! David often had the opportunity to kill King Saul, his persecutor, who was eager to destroy him. Yet when Saul was subject to him and in his power, David preferred to save his life and did not retaliate on his enemy but, on the contrary, even avenged him when he was killed. In short, many prophets have been killed, many martyrs have been honored with glorious deaths, and all have attained their heavenly crowns through the merit of patience, for a crown for sorrow and suffering cannot be obtained unless patience in sorrow and suffering precede.”
Source
373
A.D.
c. A.D. 296–373
“For the truth is not preached with swords or with darts, nor by means of soldiers, but by persuasion and counsel. But what persuasion is there where fear of the emperor prevails? Or what counsel is there, when he who withstands them receives at last banishment and death? Even David, although he was a king and had his enemy in his power, did not prevent the soldiers by an exercise of authority when they wished to kill his enemy, but, as the Scripture says, David persuaded his men by arguments, and did not allow them to rise up and put Saul to death. But [the devil], being without arguments of reason, forces all men by his power, that it may be shown to all that their wisdom is not according to God but merely human, and that they who favor the Arian doctrines have indeed no king but Caesar; for by his means it is that these enemies of Christ accomplish whatsoever they wish to do.”
Source

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“Then said Abishai to David,.... Seeing Saul fast asleep, and a spear so near him: God hath delivered thine enemy into thine hand this day: or at this time, properly it was night: now therefore let me smite him, I pray thee, with the spear; with Saul's own spear, which was stuck in the ground at his bolster. He remembered that David would not put forth his hand to stay him before, when he had an opportunity; and since now another offered, he did not move it to him to do it, but begged leave to do it himself; which he might think would be granted, since there was such a remarkable hand of Providence in it, which seemed to direct to such a step: even to the earth at once, and I will not smite him the second time; signifying, that he would give such a home blow or thrust, that the spear should pierce through him, and fasten him to the ground, that there would be no need to repeat it.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“God hath delivered thine enemy into thine hand - Here Abishai uses the same language as did David's men, when Saul came into the cave at En-gedi, (see Sa1 24:4, etc.), and David uses the same language in reply.”
1849
A.D.
1774–1849
“My. Hebrew, “the spear,” which was fixed in the ground at Saul’s pillow. Protestants, “let me smite him, I pray thee, with the spear, even to the earth, at once, and I will not smite him a second time.” (Haydock)”
1871
A.D.
1871
“Then said Abishai to David, God hath delivered thine enemy into thine hand--This midnight stratagem shows the activity and heroic enterprise of David's mind, and it was in unison with the style of warfare in ancient times. let me smite him . . . even to the earth at once--The ferocious vehemence of the speaker is sufficiently apparent from his language, but David's magnanimity soared far above the notions of his followers. Though Saul's cruelty and perfidy and general want of right principle had sunk him to a low pitch of degradation, yet that was no reason for David's imitating him in doing wrong. Besides, he was the sovereign; David was a subject. Though God had rejected him from the kingdom, it was in every way the best and most dutiful course, instead of precipitating his fall by imbruing their hands in his blood and thereby contracting the guilt of a great crime, to wait the awards of that retributive providence which sooner or later would take him off by some sudden and mortal blow. He who, with impetuous haste was going to exterminate Nabal, meekly spared Saul. But Nabal refused to give a tribute to which justice and gratitude, no less than custom, entitled David. Saul was under the judicial infatuation of heaven. Thus David withheld the hand of Abishai; but, at the same time, he directed him to carry off some things which would show where they had been, and what they had done. Thus he obtained the best of victories over him, by heaping coals of fire on his head.”
Source
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.