Hadith.4274 - Al-Ala narrated from Muhammad ibn Muslim, from one of the Imams (as), that he was asked about a woman who vowed to donate all her wealth as an offering and to set all her slaves free if she ever spoke to her sister again.
Imam (as) said
"She may speak to her, and this (vow) is of no consequence. Indeed, this and similar actions are among the steps of Satan."