'Widow' in the Bible

"Teacher, Moses wrote for us that if a man's brother dies and leaves a wife but no child, he should marry the widow and have children for his brother.

And there came a certain poor widow, and she threw in two mites, which make a farthing.

And he called unto him his disciples, and saith unto them, Verily I say unto you, That this poor widow hath cast more in, than all they which have cast into the treasury: