بُلُوغُ الْمَرَامِ
Bulugh al-Maram 422
The Book of Prayer
وَعَنْ أَبِي هُرَيْرَةَ - رضى الله عنه - عَنْ اَلنَّبِيِّ - صلى الله عليه وسلم -قَالَ: { إِذَا سَمِعْتُمْ اَلْإِقَامَةَ فَامْشُوا إِلَى اَلصَّلَاةِ, وَعَلَيْكُمْ اَلسَّكِينَةُ وَالْوَقَارُ, وَلَا تُسْرِعُوا, فَمَا أَدْرَكْتُمْ فَصَلُّوا, وَمَا فَاتَكُمْ فَأَتِمُّوا } مُتَّفَقٌ عَلَيْهِ, وَاللَّفْظُ لِلْبُخَارِيِّ . [1] .
Narrated Abu Hurairah (RA): The Prophet (ﷺ) said: "If you hear the Iqamah, you must walk to the prayer (place) with tranquility and dignity, and do not hasten; and whatever portion of the prayer you get (along with the Imam) offer it, and complete afterwards whatever you missed. [Agreed upon, and the wording is al-Bukhari's).
Sunnah.com reference: Book 2, Hadith 329