Hebrews 12:11

Discipline always seems for the time to be a thing of pain, not of joy; but those who are trained by it reap the fruit of it afterwards in the peace of an upright life.

Matthew 10:37

He who loves father or mother more than me is not worthy of me; he who loves son or daughter more than me is not 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
He who loves father or mother more than me is not worthy of me; he who loves son or daughter more than me is not worthy of me:
Hebrews 12:11
Discipline always seems for the time to be a thing of pain, not of joy; but those who are trained by it reap the fruit of it afterwards in the peace of an upright life.