Abdullah b. Abu Qatada reported on the authority of his father: While we said our prayer with the Messenger of Allah (ﷺ) he heard tumult. (At the end of the prayer) he (the Holy Prophet) said: What is the matter with you? They said: We hastened to prayer. He (the Holy Prophet) said: Don't do that; when you come for prayer, there should be tranquillity upon you. Pray (along with the Imam) what you can find and complete what preceded you.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنِي إِسْحَاقُ بْنُ مَنْصُورٍ، أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُبَارَكِ الصُّورِيُّ، حَدَّثَنَا مُعَاوِيَةُ بْنُ سَلاَّمٍ، عَنْ يَحْيَى بْنِ أَبِي كَثِيرٍ، أَخْبَرَنِي عَبْدُ اللَّهِ بْنُ أَبِي قَتَادَةَ، أَنَّ أَبَاهُ، أَخْبَرَهُ قَالَ بَيْنَمَا نَحْنُ نُصَلِّي مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَسَمِعَ جَلَبَةً . فَقَالَ " مَا شَأْنُكُمْ " . قَالُوا اسْتَعْجَلْنَا إِلَى الصَّلاَةِ . قَالَ " فَلاَ تَفْعَلُوا إِذَا أَتَيْتُمُ الصَّلاَةَ فَعَلَيْكُمُ السَّكِينَةُ فَمَا أَدْرَكْتُمْ فَصَلُّوا وَمَا سَبَقَكُمْ فَأَتِمُّوا " .
sunnah.com