Allah Ta'ala says in Bani Israil:
And your Lord has commanded you not to worship anyone other than Allah and treat the parents with benevolence. If either or both of them attain to old age in your presence, then do not say even ‘Ugh!’ to them nor reproach them. And always speak to both of them submissively, observing polite manners. And always lower your arms of submissiveness and humility out of soft-heartedness for both of them and keep supplicating (Allah): ‘O my Lord, have mercy on both of them as they brought me up in (my) childhood (with mercy and clemency).’ Surah Isra (17:23/24)
In this verse, Allah Ta'ala has given us 7 commands, 5 of them are to be performed and 2 of them are to be refrained from.
Those which are to be performed are:
1. We should worship only Allah Ta'ala.
2. Treat parents nicely.
3. To talk to parents with appropriate respect.
4. To be soft and humble before them.
5. We should pray for our parents with the words: "Lord! Have mercy on them as they brought me up with love and affection in my childhood."
Those things which are to be avoided:
1. We should not even say "Uff" to the parents, i.e. we should not fume or fret before them.
2. We should talk to parents with disrespect.
It should be noted that the command to respect parents is being given because they are the means of the children coming into this world. Thus, their respect and reverence is compulsory on the children. When we appear before them, our eyes should be lowered, we should talk to them softly, we should not scold them nor speak severely to them. Leave alone hurting them with our words, we should not even say "Uff" to them. We should consider that when we are asked to respect our parents, who are the means of coming into this world, in such a manner, then how much should we respect the Holy Prophet (Sallallahu alaihi wa sallam) who is the very reason for the existence of this universe?
The approval of parents is the approval of Allah Ta'ala
There is a Hadith in Kanz Ul Ummal:
It has been narrated on the authority of Hadhrat Abdullah Bin Umar (May Allah Ta'ala be well pleased with him) that the Holy Prophet (Sallallahu alaihi wa sallam) said: The approval of Allah Ta'ala is in the pleasure and approval of Allah Ta'ala and the displeasure of Allah Ta'ala is in the displeasure of the father. (Kanz Ul Ummal, Hadith No. 45552)
The importance of treating one's mother well
There is a Hadith in Sahih Bukhari:
It has been narrated on the authority of Hadhrat Abu Hurairah (May Allah Ta'ala be well pleased with him), he said that a certain Sahabi came to the Holy Prophet (Sallallahu alaihi wa sallam) and asked: O Prophet of Allah (Sallallahu alaihi wa sallam)! Who is the most deserving of my kind treatment? He (Sallallahu alaihi wa sallam) said: Your mother is the most deserving of it. He said: Then whom? He (Sallallahu alaihi wa sallam) said: Your mother is the most deserving of it. He said: Then whom? He (Sallallahu alaihi wa sallam) said: Your mother is the most deserving of it. When he asked this for the 4th time, He (Sallallahu alaihi wa sallam) said: Your father is most deserving of your kind treatment. (Sahih Bukhari, Hadith No. 5971.
The Holy Prophet (Sallallahu alaihi wa sallam) gave the service of the mother 3-fold excellence than the service of the father as the mother passes through 3 phases in which the father does not participate at all. One is the phase of pregnancy, secondly, the phase of labor and childbirth and thirdly, the phase of breastfeeding/nursing.
In the interpretation of this Hadith, Allama Badruddin Aini Hanafi (May Allah Ta'ala shower His mercy on him) writes:
Translation: Muhaddith Tammam narrates on the authority of Hadhrat Abdullah Bin Abbas (May Allah Ta'ala be well pleased with them) that a Sahabi came to the Holy Prophet (Sallallahu alaihi wa sallam) and said: I had taken a vow that when Allah Ta'ala conquers Makkah for you, I would go there and kiss the doorsill of the Ka'aba. The Holy Prophet (Sallallahu alaihi wa sallam) said: You kiss the feet of your mother. Indeed! You will have fulfilled your vow. ('Umdatul Qari, Vol. 15, Pg. No. 141)
Jannah lies under the feet of the mother
It has been narrated on the authority of Hadhrat Anas (May Allah be well pleased with him) that:
Translation: Jannah is under the feet of the mother.
Imam Sakhawi (May Allah shower His Mercy on him) has narrated this Hadith in Maqasidul Hasana and has mentioned that Khateeb has narrated this Hadith in his Jame’ (compendium) and Muhaddith Qazai has narrated this in his own Musnad.
(Maqasudul Hasana, Harful Jeem)
It is mentioned in Sunan Nasai, Kitabul Jihad:
Translation: It has been narrated on the authority of Hadhrat Muawiya bin Jahima (May Allah be well pleased with him) that Hadhrat Jahima (May Allah be well pleased with him) presented to the Holy Prophet (Sallallahu alaihi wa sallam) and entreated: O Prophet of Allah SWT! I want to participate in a Ghazwah (i.e. in a battle along with the Holy Prophet (Sallallahu alaihi wa sallam)) and have come to You to seek Your permission. Then the Holy Prophet (Sallallahu alaihi wa sallam) said: Do you have a mother? He said: Yes. The Holy Prophet (Sallallahu alaihi wa sallam) said: You stay with her and serve her, because Jannah is under her feet.
Hadhrat Mulla Ali Qari (May Allah shower His Mercy on him) writes in the interpretation and explanation of this Hadith in Mirqatul Mafateeh, Vol. 4, Pg No: 677:
Translation: Jannah is under the feet of the mother means that we should behave with utmost humility and respect with the mother.
He also writes: ‘Jannah is under the feet of the mother’ the import of this Hadith is that obedience to the mother, treating her nicely and bearing difficulties and hardships in this regard lead one in to the bountiful Jannah.
What does treating the mother nicely mean?
If the mother is alive, then treating her nicely means that they should be served and their commands should be followed. When she passes away, then treating her nicely means that we should pray for her forgiveness, if there was any debt on her, it should be paid off, her relatives should be treated considerately and we should do Isaal-e-Sawab i.e. performing good deeds and gift the reward to them.