Because the Lord disciplines those he loves, as a father the son he delights in (Proverbs 3:12 NIV).
For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life (John 3:16).
Greater love has no one than this, that someone lay down his life for his friends (John 15:13 ESV).