Charles Spurgeon Commentary 1 Samuel 18

And it came to pass, when he had made an end of speaking unto Saul, that the soul of Jonathan was knit with the soul of David, and Jonathan loved him as his own soul.

Jonathan, the brave young soldier who had himself done great exploits, naturally admired the youthful warrior who had slain the Philistine giant, and also admired the modesty of his speech when he returned with the head of Goliath in his hand: The soul of Jonathan was knit with the soul of David, and Jonathan loved him as his own soul.

And Saul took him that day, and would let him go no more home to his father's house. Then Jonathan and David made a covenant, because he loved him as his own soul. And Jonathan stripped himself of the robe that was upon him,

No doubt, one suitable to his rank as the heir apparent to the throne of Israel.

And gave it to David, and his garments, even to his sword, and to his bow, and to his girdle. And David went out whithersoever Saul sent him, and behaved himself wisely: and Saul set him over the men of war,

Probably, Jonathan had previously occupied that position; but now that David is called to supplant him, Jonathan is not jealous of him, but he loves him as he loves his own soul.

And he was accepted in the sight of all the people, and also in the sight of Saul's servants. And it came to pass as they came, when David was returned from the slaughter of the Philistine, that the women came out of all cities of Israel, singing and dancing, to meet king Saul, with tabrets, with joy, and with instruments of music.

And the women answered one another as they played, and said,-

Singing in chorus, with answering refrains,-

Saul has slain his thousands, and David his ten thousands.

And Saul was very angry, and the saying displeased him; and he said, They have ascribed to David ten thousands, and to me they have ascribed but thousands: and what can he have more but the kingdom? And Saul eyed David from that day onward.

This shows how envy will destroy a person's own peace of mind, as well as make them plot against the one they envy.

Instead of being thankful to God for sending him such a valiant champion as David to deliver both himself and his people, Saul is full of malice towards the young hero simply because he receives his due praise for his victory over the giant. "Saul eyed David" with an evil and envious eye; he looked askance at him, and determined to do him harm whenever he could.