Yevamos 87b: Once a widow is exempted from Yibum she is always exempt, even if her husband's children die. (It would not be pleasant if afterwards she is obligated to do Yibum or Chalitzah.)

Yevamos 15a: What should we do for Tzaros of Beis Hillel (who remarried without Chalitzah), according to Beis Shamai? If we require them to do Chalitzah, their husbands will despise them! We cannot do so, for "(Torah's) ways are pleasant... its paths are Shalom!"

Gitin 59b: All laws of the Torah are for Darchei Shalom.

Malbim: Derech is the path for the Rabim. The general paths of Chachmah lead to No'am - spiritual pleasantness that one gets when he attains the purpose. One who engages in this is satiated with brightness of the Nefesh. Nesivos are paths for individuals that branch off the big path. Every individual goes on a path to conduct himself and his household. These are Shalom. Shalom of the body, house, country and his acquisitions depend on his individual conduct in special paths of Chachmah that depart from the big path.