Hebrews 12:11

Now all chastning for the present is assuredly not joyous, but grievous; yet afterwards it yieldeth the peaceable fruit of righteousness to them that are exercised thereby.

Matthew 10:37

He that loveth father or mother more than me, is not worthy of me, and he that loveth 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 that loveth father or mother more than me, is not worthy of me, and he that loveth son or daughter more than me, is not worthy of me;
Hebrews 12:11
Now all chastning for the present is assuredly not joyous, but grievous; yet afterwards it yieldeth the peaceable fruit of righteousness to them that are exercised thereby.