Muwatta Malik #545
Burials
The Arabic includes the chain of narration (sanad) and the collector's commentary; the English translation shows the Prophet's words only.
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ سَأَلَ ابْنَ شِهَابٍ عَنِ الرَّجُلِ، يُدْرِكُ بَعْضَ التَّكْبِيرِ عَلَى الْجَنَازَةِ وَيَفُوتُهُ بَعْضُهُ فَقَالَ يَقْضِي مَا فَاتَهُ مِنْ ذَلِكَ .
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."
About Muwatta Malik
This hadith is #545 from Muwatta Malik, in the Book of Burials.