صَاحِبْهُمَا فِي الدُّنْيَا مَعْرُوفًا (And be with them, in this world, with due fairness - 15).
It means: 'In the matter of the contravention of your faith and religion, do not obey parents. But, when it comes to worldly matters, such as serving parents physically or financially or in any other way necessary, do not fall short about it. Instead, deal with them in mundane matters according to recognized custom. Show no disrespect to them. Do not respond to what they say in a manner that hurts them unnecessarily. In other words, the pain you cause them by not accepting their insistence on Shirk and Kufr is something you will have to bear by, since you have no choice there. But, let this necessity stay within its functional limits and keep abstaining from causing any pain to them in other matters.'
Special Note
As for the weaning period of two years for a child mentioned in the verse, it is in accordance with customary practice. It carries no clarification concerning the injunction relevant to any additional period of suckling the child. A detailed explanation of this issue will, insha'Allah, appear under the commentary on the verse: وَحَمْلُهُ وَفِصَالُهُ ثَلَاثُونَ شَهْرًا (And his carrying and weaning is (in) thirty months - A1-Ahgaf, 46:15).