اللّهُـمَّ إِنَّـي أَسْـأَلُـكَ خَيْـرَها، وَأَعـوذُ بِكَ مِنْ شَـرِّها
Allaahumma innee as aluka khayrahaa, wa a oothu bika min sharrihaa.
O Allah, I ask You for the good of it and seek refuge in You against its evil.
Reference:
Abu Dawud 4/326, Ibn Majah 2/1228. See also Al-Albani, Sahih Ibn Mjjah 2/305