On any day when Hallel is recited there is no maamad at Shacharis. [Whenever there is] a musaf-sacrifice, there is no [maamad even] at Ne'ilah. [Whenever there is] a wood-offering, there is no [maamad] at Minchah. [This is] R' Akiva's view. Ben Azzai said to him, “R' Yehoshua would learn this way: `[Whenever there is a] musaf-sacrifice, there is no [maamad] at Minchah; [whenever there is] a wood-offering, there is no [maamad] at Ne'ilah.' ” R' Akiva retracted in order to comply with Ben Azzai.