Silsilah as-Sahihah 1220 — Oath causing harm to family is forbidden

Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Noble Prophet (peace and blessings of Allah be upon him) said: "When a man swears an oath regarding his family and (in his own estimation) pretends to be truthful, then he will be more sinful in the sight of Allah than (by paying) that expiation which Allah has commanded him."