Muwatta Imam Malik Book of Burials, Hadith 16
Yahya related to me that Malik asked Ibn Shihab about a man who caught some of the takbirs said over the corpse and missed the rest, and Ibn Shihab said, "He completes what he has missed."
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ سَأَلَ ابْنَ شِهَابٍ عَنِ الرَّجُلِ، يُدْرِكُ بَعْضَ التَّكْبِيرِ عَلَى الْجَنَازَةِ وَيَفُوتُهُ بَعْضُهُ فَقَالَ يَقْضِي مَا فَاتَهُ مِنْ ذَلِكَ .