ואקחה פת לחם היה לו לומר קחו פת לחם מכאן רמז שבעל הבית בוצע: "And I will fetch a morsel of bread" - It would have been sufficient for him to say, "Take a morsel of bread." From here we learn that the host should be proactive.
לבכם ג' במסורה הכא ואידך שיתו לבכם לחילה. וראיתם ושש לבכם. וזהו שאמרו שהיה מצטער על שלא באו לו אורחים וזהו שיתו לבכם שהיה מצטער בלבו כיון שראה אלו ושש לבכם: Your hearts [לבכם] - three [words] in the Tanakh here and there [in the text]. [It means] "set your heart to worry." "וראיתם ושש לבכם" - "and you shall see, and your heart will be glad." This is [to teach us] that [Abraham] was pained that guests had not come to him, and this is [why it says] "set your heart to worry," that he was worried in his heart when he saw them, and "your heart will be glad," as his heart was gladdened [when they arrived].