The closest to a person are his parents. Allah (جل جلاله) in many verses of the Quran commands to serve the parents. Twelve verses of the Quran emphasize this service. With respect to the upbringing of their children, the parents are a clear sign of Allah's Mercy. 

He (جل جلاله) says:

و إذا أخذنا ميثاق بني إسرائيل لا تعبدون إلا الله و بالوالدين إحسانا

And remember We took a covenant from the Children of Israel (to this effect): Worship none but Allah; treat with kindness your parents [2: 83] He (جل جلاله) also says:

و قضي ربك ألا تعبدوا إلا إياه و بالوالدين إحسانا إما يبلغن عندك الكبر أحدهما أو كلاهما فلا تقل لهما أف و لا تنهرهما و قل لهما قولا كريما –و أخفض لهما جناح الذل من الرحمة و قل رب إرحمهما كما ربياني صغيرا

Your Lord has decreed that you worship none but Him, and that you be kind to parents. Whether one or both of them attain old age in your life, say not to them a word of contempt, nor repel them, but address them in terms of honor. And, out of kindness, lower to them the wing of humility, and say: "My Lord! Bestow on them your Mercy even as they cherished me in childhood." [17:23-24] Allah's (جل جلاله) order is that:

و وصينا الإنسان بوالديه إحسانا

We have enjoined on man kindness to his parents. [46:15] Even the non-believing (poly-theist) parents must be dealt with kindly:

و صاحبهما في الدنيا معروفا

Bear them company in this life with justice (and consideration.) [31:15] Another place in the Quran, it says:

و وصينا الإنسان بوالديه إحسانا حملته أمه كرها و وضعته كرها و حمله و فصاله ثلاثون شهرا

We have enjoined on man kindness to his parents: In pain did his mother bear him, and in pain did she give him birth. The carrying of the (child) to his weaning is (a period of) thirty months. [46:15] Muhammad (صلى الله عليه وسلم) once said that:

ما من ولد بار ينظر إلي والديه نظر رحمة إلا كتب الله بكل نظرة حجة مبرورة قالوا و إن نظر كل يوم مائة نظرة قال نعم الله و أكبر و أطيب

(مشكوة –باب البر و الصلة-شعب الإيمان و البيهقي)

If a son or daughter looks at his parents with love and mercy, Allah grants him/her the reward of an accepted Hajj. He was asked even if that happened a hundred times a day. The reply was in affirmative; Allah is the Greatest and free of any imperfection. This just states the incentive of looking at one's parents lovingly; serving them earns one even more of His blessings. A companion of the Prophet (صلى الله عليه وسلم) once sought his advice about taking part in a battle. The Prophet (صلى الله عليه وسلم) said:

هل لك من أم قال نعم قال فألزمها فإن الجنة عند رجلها

(مشكوة-ص421-نسائي،مسند أحمد)

"Is your mother alive?" The companion said, "Yes." He was told to stay with his mother because the Paradise was under her feet. One of his companions asked the Prophet (صلى الله عليه وسلم):

ما حق الوالدين علي ولدهما هما جنتك و نارك

(مشكوة-ص1221-إبن ماجة)

What are the rights of parents on their children?" He (صلى الله عليه وسلم) replied that they were his Paradise or his Hell. This means that being obedient (while staying within the boundaries of Islam) to one's parents can result in Paradise as one's destination. 

Link: http://www.scholaris.com/islam/learning/PDF/Islam-TheReligionOfMercy.pdf