1 Samuel 20:17

And Jonathan again made David swear an oath, because he loved him; for with the love of his soul he loved him.

1 Samuel 18:1

{When} he finished speaking to Saul, the soul of Jonathan became attached to the soul of David, and Jonathan loved him as his [own] soul.

1 Samuel 18:3

Then Jonathan made a covenant with David, because he loved him as his [own] soul.

Deuteronomy 13:6

"If your brother, the son of your mother or your son or your daughter {or your wife whom you embrace} or {your intimate friend} in secrecy {says}, 'Let us go and let us serve other gods!' [gods] that you and your ancestors have not known,

2 Samuel 1:26

{I am distressed} over you, my brother Jonathan. you [were] very dear to me; your love [was] more wonderful to me than the love of women.

Proverbs 18:24

A man of [many] friends will come to ruin, but there is a friend who sticks closer than a brother.

Treasury of Scripture Knowledge

Summary

And Jonathan caused David to swear again, because he loved him: for he loved him as he loved his own soul.

General references

Bible References

Because he loved him

1 Samuel 18:1
{When} he finished speaking to Saul, the soul of Jonathan became attached to the soul of David, and Jonathan loved him as his [own] soul.
Deuteronomy 13:6
"If your brother, the son of your mother or your son or your daughter {or your wife whom you embrace} or {your intimate friend} in secrecy {says}, 'Let us go and let us serve other gods!' [gods] that you and your ancestors have not known,
2 Samuel 1:26
{I am distressed} over you, my brother Jonathan. you [were] very dear to me; your love [was] more wonderful to me than the love of women.
Proverbs 18:24
A man of [many] friends will come to ruin, but there is a friend who sticks closer than a brother.

General references

1 Samuel 23:18
Then the two of them {made} a covenant before Yahweh. David remained at Horesh, and Jonathan went to his house.
Proverbs 17:17
The friend loves at all times, but a brother is born for adversity.