Sometimes women will light candles and accept the Shabbos a few minutes earlier than usual as a zchus for a sick person. How does accepting Shabbos early act as a zchus? How does it compare with davening for the choleh or saying Tehillim?
The Imrei Emes is quoted as saying,
By adding more kedushah of Shabbos to the home, one increases holiness and purity to the family. This has the potential spiritual power to counteract some of the impurities that a child may have engaged in and bring him closer to purity. The more we widen the boundaries of kedushah, the more narrow the territory of tumah becomes. This is the power of tosefes Shabbos.