The Shaykh’s explanation that it is from the Sunnah for the imam not to raise his voice with the taslim in the funeral prayer.

The questioner : The Sunnah regarding the taslim is…

The Shaykh : There are two taslims, as in the other prayers, but the funeral prayer is distinguished from the other prayers in that the imam does not raise his voice with the taslim. This is a wisdom that must be submitted to. The imam in the funeral prayer says the taslim to the right and to the left, but he does not raise his voice audibly, as is the Sunnah in the obligatory prayers. He says the taslim quietly. Without a doubt, the taslim will proceed from right to left. The second row, which follows the first row, notices that those in front of them have said the taslim to the right and to the left, and so on. Let no one say, “How are we supposed to say the taslim?” because this is a matter that is obvious to the eye. Every second row sees the first row, and the third row sees the second row, and so on. The important point is that the funeral prayer has two taslims. What some people say, that the funeral prayer is specific to a single taslim, has no basis in the Sunnah. Yes, in the Sunnah generally, in all prayers, it is permissible for the worshipper to limit himself to a single taslim, because that single taslim takes the worshipper out of the prayer. But the complete Sunnah is to also say the taslim to the left. There is no difference in this between the five obligatory prayers and the funeral prayer. So, adhering to a single taslim only in the funeral prayer has no basis in the Sunnah. All that can be said is that it is permissible to limit oneself to a single taslim in the funeral prayer, just as in the obligatory prayers. But the better practice in the obligatory prayers and in the funeral prayer is two taslims, as you will see, and I do not say “as you will hear,” because you will not hear the taslim audibly; rather, you will notice, if Allah wills, as we mentioned earlier.