From Sahih Muslim (Hadith 3693):
Ibn Abbas (Allah be pleased with them) said:I came along with Umar until we reached Marr al-Zahran (the name of a place), and the rest of the hadith is the same as narrated by Sulaiman b. Bilal (except with) the variation (of words) that I said: (What) about these two women? He said: They were Hafsa and Umm Salama. And he made this addition: I came to the apartments and in every apartment there was (the noise) of weeping. And this addition was also made: And he (the Holy Prophet) had taken an oath of remaining away from them for a month, and when twenty-nine days had passed, he visited them
Reference: Muslim 3693