The Suitable Age For Marriage
I advise young women not to refuse marriage from a man due to his age, such as being ten, twenty or thirty years older than her. This is not a reason, because the Prophet, sallallaahu alayhi was salam, married 'A'ishah, may Allaah be pleased with her, when he was fifty-three years old and she was a girl of nine years old. So being older does not harm. There is no sin in the woman being older, nor any sin in the man being older, because the Prophet, sallallaahu alayhi was salam, married Khadijah, may Allaah be pleased with her, when she was forty years old and he was twenty-five years old, before the Revelation came to him, sallallaahu alayhi was salam; that is, she, may Allaah be pleased with her, was fifteen years older than him. Then he married 'A'ishah, may Allaah be pleased with her, when she was small - six or seven years old and he was fifty-three years old.
Many of those who speak on the radio or television deter people from marriage between men and women of differing ages - this is all wrong & saying such things is not permissable for them. It is obligatory for a woman to look at the (prospective) husband, and if he is righteous and suitable, she should agree, even if he is older than her. Similarly, a man should devote himself to finding a righteous, religious woman, even if she is older than him, if she is still young and still fertile. In short, the age should not be an excuse and it should not be considered something shameful, as long as the man is righteous and the woman is righteous. May Allaah reform the situation of us all.
Shaykh `Abdul-`Azeez Bin Baz
Fatawa Islamiyah, volume 5, The Book of Marriage, page 169-170