Muwatta Malik Book 8, Hadith 9
Yahya related to me from Malik from Zayd ibn Aslam from a man of
the Bani'd-Dil called Busr ibn Mihjan from his father Mihjan that he
was in a gathering with the Messenger of Allah, may Allah bless him
and grant him peace, and the call to prayer was made. The Messenger of
Allah, may Allah bless him and grant him peace, rose and prayed and
then returned. Mihjan remained sitting and did not pray with him. The
Messenger of Allah, may Allah bless him and grant him peace, said,
"What prevented you from praying with the people? Aren't you a
muslim?" He said, "Of course, Messenger of Allah, but I have already
prayed with my family." The Messenger of Allah, may Allah bless him
and grant him peace, said, "When you come, pray with the people, even
if you have prayed already."
Yahya related to me from Malik from Yahya ibn Said from Muhammad ibn Ibrahim that Abd ar-Rahman ibn Abi Amra al-Ansari said that Uthman ibn Affan came to the isha prayer and seeing only a few people in the mosque, he lay down at the back of the mosque to wait for the number of people to increase. Ibn Abi Amra went and sat down beside him and Uthman asked him who he was, so he told him. Uthman said, "What have you memorised of the Qur'an?", and he told him. Uthman said, "If someone is present at isha, it is as if he had stood in prayer for half a night, and if some one is present at subh, it is as if he had stood in prayer for a whole night.
Yahya related to me from Malik from Nafi that a man asked Abdullah ibn Umar, "Sometimes I pray in my house, and then catch the prayer with the imam. Should I pray with him?" Abdullah ibn Umar said to him, "Yes," and the man said, "Which of them do I make my prayer?" Abdullah ibn Umar said, "Is that up to you? It is up to Allah. He will decide on whichever of them He wishes."