Sunan an-Nasa'i

It was narrated from Abu Qilabah that a man said: "I came to the Prophet to discuss something and he was eating breakfast. He said: “Come and eat.' I said: “I am fasting.' He said: “Come and I will tell you about fasting. Allah has waived half of prayer and fasting from the traveler, and he has granted a concession to pregnant women and the sick”””"