Islam has greatly emphasized the issue of loving and respecting the parents, the father and the mother. In our infancy and childhood, we needed the protection, love and nurturing of the parents; but when they become old, they need us to protect them and take care of them.
"Your Lord has commanded that you shall not worship (anyone) but Him and to be good to the parents. If either or both of them reach old age with you, say not to them (so much as) 'Ugh' nor chide them, and speak to them a generous word. And lower for them 'the wings of humility' out of mercy; and pray; 'O my Lord! Have mercy on them as they brought me up (when I was) little.'" [Al-Isra'(17):23-24]
However, out of the two, the mother has been given greater priority as far as kindness is concerned. Once Hakim bin Hizam came to the Prophet of Islam and asked: "To whom should I be kind?" The Prophet replied, "Your mother." Hakim asked, "Then to whom?" The Prophet said, "Your mother." Hakim asked, "Then to whom?" The Prophet replied, "Your mother." Only when Hakim asked the fourth time that, "Then to whom?" the Prophet replied, "Your father." This shows that the right of mother upon the children is three times more than the rights of father as far as kindness is concerned.
And the paradise is under the feet of your mothers. - Prophet Muhammad (peace be upon him)
[Ibne `Abbas states:] “I questioned the Messenger of Allah (peace be upon him and his family): Which deed is the most beloved in the eyes of Allah, the Mighty, the Glorious?” He (peace be upon him and his family) replied: “(Offering) prayers at their stipulated times.” I then asked: “Which is the next most beloved deed?” He (peace be upon him and his family) answered: “Goodness towards (one’s) parents.” I asked him again: “After this which is the most beloved act?” He (peace be upon him and his family) said: “Jihad in the way of Allah.” [1]
The Messenger of Allah (peace be upon him and his family) said: “Every righteous child who casts a look of mercy and affection upon his parents shall be granted, for every look of his, rewards equivalent to that of an accepted Hajj.” Those around the Prophet questioned: “O’ Prophet of Allah! Even if he were to look at them a hundred times a day?” The Messenger of Allah (peace be upon him and his family) replied: “Indeed! Allah is the Greatest and Most Kind.” [2]
{1] and [2] - http://www.al-islam.org/FortyParents/