Hebrews 12:11

Discipline is never pleasant at the time; it is painful; but to those who are trained by it, it afterward yields the peace of character.

Matthew 10:37

No one who loves father or mother more than he loves me is worthy of me, and no one who loves son or daughter more than he loves me is worthy of me,

Treasury of Scripture Knowledge

Summary

And the thing was very grievous in Abraham's sight because of his son.

Bible References

Because

Matthew 10:37
No one who loves father or mother more than he loves me is worthy of me, and no one who loves son or daughter more than he loves me is worthy of me,
Hebrews 12:11
Discipline is never pleasant at the time; it is painful; but to those who are trained by it, it afterward yields the peace of character.