Mr Mugabe made his first public comments on last week's fatal crash, reportedly telling mourners at Tuesday's church service: "I plead with you to accept it, it's the hand of God."
Suspicions have swirled over Mrs Tsvangirai's death given past acrimony between the prime minister and president.
But Mr Tsvangirai said on Monday it was unlikely foul play took a part in the collision, which involved an aid lorry.
How a convoy of three vehicles, with one in the middle carrying the second most important person in the land, got involved in a car crash, is what has perplexed many people.
The oncoming lorry, which apparently belonged to a partner of the US government aid agency USAID, is thought to have crossed into the prime minister's path, sideswiping the right bumper of Mr Tsvangirai's Land Cruiser, which then rolled off the highway.