Rebbe Tarfon helping mother climb up and down the bed:
Rebbe Tarfon had a mother whom whenever she desired to climb up to her bed he would bend down and have her climb on his back, and whenever she desired to go down from the bed she would climb down onto his back. When Rebbe Tarfon came to the house of study, he bragged of the great honor that he has for his mother. The students present responded to him that he is not yet reach even half of that which is required to be done to honor one’s parents.
In the Jerusalem Talmud we find another similar story: One time when the mother of Rebbe Tarfon went down to her yard for a walk on Shabbos and her sandals broke and Rebbe Tarfon placed his hands under his mother’s feet in order to help her walk to her bed. The sages responded about this that even if he does hundreds of thousands as such, he is still not reached half of the honor the Torah requires one to show his parents.
Nevertheless, this extent of honor as shown by Rebbe Tarfon is not an actual obligation, but rather a Midas Chassidus for which one receives reward but does not get punished if he does not fulfill.
 Kiddushin 31b
 Yerushalmi Peiah 1:1; Kiddushin 1:7; Meiri Kiddushin 31a; See Encyclopedia Talmudit Erech Kibud Av Vaeim Vol. 26 footnote 88
 Rishon Letziyon 240:7; Meshivas Nefesh 1:16-9; See Ran Kiddushin 33b