I heard Anas bin Malik say, "Whenever we stopped at a place to camp, we would not perform the voluntary prayers until the saddles had been unloaded."
حدثنا محمد بن المثنى حدثني محمد بن جعفر حدثنا شعبة
سمعت أنس بن مالك قال كنا إذا نزلنا منزلا لا نسبح حتى تحل الرحال
[Its isnad is sahih] Ahmad reported it in 3/29, from Muhammad bin Jafar Ghundar, through this chain.