Ibn `Abbas (radiallahu `anh) said:
There are three verses in the Qur`an which are associated with three things and none is accepted if the other is missing.
The first one:
Allah says {obey Allah and obey the Messenger};
so whomever obeys Allah but disobeys the Messenger (salallahu alayhe wassallam), his obedience to Allah will not be accepted.
The second one:
Allah says {Offer salaat and give zakaat};
so whoever offers salaat but refuses to give zakaat. Allah will not accept from him.
The third one:
Allah says {give thanks to me and to your parents};
so whoever gives thanks to Allah and does not give it to his parents, Allah will not accept that from him. Therefore, the Prophet (salallahu `alayhe wassallam) said: ‘If your parents are pleased with you, Allah too will be pleaed with you, and if your parents are displeased with you, Allah too will be displeased with you. “
Imam adh-Dhahabi ‘al-Kaba`ir’
بسم الله الرحمن الرحيم 