The incident occurred yesterday in Khanewal district, 350 km from Lahore, the capital of Punjab.
According to police, Abid Husain, a farmer, quarrelled with his wife Rukhsana over going to a relative's house to attend a 'qul' (prayer for the dead).
Rukhsana wanted to go to the event with Husain as her parents too were coming there but he refused.
Police said when Husain left the house, Rukhsana allegedly gave milk laced with poison to her three children - Rizwana Bibi (3), Majid (2), and baby girl aged about two weeks.
A murder case was registered against Rukhsana, police said.
