Here are 2 Bible verses about mother in law from the Old and New Testaments of the Holy Bible (King James Version), sorted from most to least relevant.
John 19:26-27 KJV
When Jesus therefore saw his mother, and the disciple standing by, whom he loved, he saith unto his mother, Woman, behold thy son! Then saith he to the disciple, Behold thy mother! And from that hour that disciple took her unto his own home.
2 Timothy 1:5 KJV
When I call to remembrance the unfeigned faith that is in thee, which dwelt first in thy grandmother Lois, and thy mother Eunice; and I am persuaded that in thee also.