Laborers doing work for their employer should abbreviate the grace after meals so that they do not take themselves away from the work of their employer. How (do they abbreviate the grace after meals)? (They recite) the first blessing as established and the second they begin with "the blessing on the land" then include in it "He who builds Jerusalem" and conclude with "the blessing on the land". They do not recite the blessing of "The one who is Good and does good" at all. In what circumstances does this apply? When they are receiving payment for their work besides the meal (they are provided with). However, if they are not taking payment but rather are only provided with the meal they eat, they should recite all four blessings as established. This is also the case if the employer is eating with them, even if they are taking payment in addition to the meal, they should recite all four blessings.
The Gemara notes that this disagrees with what an angel said. As an angel found Rav Ketina when he was wearing a linen cloak, which is exempt from ritual fringes. The angel said to him: Ketina, Ketina, if you wear a linen cloak in the summer and a coat [sarbela], which has only two corners and is therefore also exempt from ritual fringes, in the winter, what will become of the ritual fringes of sky-blue wool? As a result, you will never fulfill the mitzva.
It is forbidden to deliberately close one’s eyes before he reaches within four cubits in order to avoid having to stand up for him when he comes closer.
The baraita continues: One might have thought that one may close his eyes like one who does not see the elder. Therefore, the verse states: “Before the hoary head you shall stand and you shall revere the face of an elder, and you shall fear your God” (Leviticus 19:32). With regard to any matter given over to the heart, it is stated: “And you shall fear your God.” This phrase is referring to a situation where it is impossible to prove whether one purposefully made it appear as if he were not aware that he was obligated to perform a mitzva, as only that individual and God know the truth.