Muwatta Malik Book 7, Hadith 26
Yahya related to me from Malik that Yahya ibn Said said, ''Ubada
ibn as-Samit used to lead the people in prayer. One day he came out
for subh and the muadhdhin began to give the iqama for the subh prayer
Ubada silenced him, prayed witr and then led them in subh."
Yahya related to me from Malik from Hisham ibn Urwa from his father that Abdullah ibn Masud said, "I do not mind if the iqama for the subh prayer is called while I am still praying witr."
Yahya related to me from Malik that Abd ar-Rahman ibn al-Qasim said, "I heard Abdullah ibn Amir ibn Rabia say, 'I sometimes pray witr while hearing the iqama, or after the break of dawn.' " Abd ar-Rahman was not certain which he said.