Valmiki Ramayana Ayodhya Kanda Sarga 74 Shloka 15

अन्यदा at some other time, धर्मज्ञा conversant with righteous ways, सुरसम्मता highly respected by the gods, सुरभिः Surabhi (the divine cow), उर्व्याम् on the earth, वहमानौ carrying the burden (drawing the plough), विगतचेतसौ senses lost, पुत्रौ sons, ददर्श किल beheld, as they say.

It is said that once upon a time Surabhi, the divine cow, highly respected by the gods and conversant with righteous ways, beheld her two sons who fainted due to fatigue while carrying the burden of the ploughs.