These are the opening words of the "Subtrahente se famula Christi Liudmila" excerpt from Legenda Christiani (Vita et passio sancti Wenceslai et sanctae Ludmilae avae eius). However, what is the scribal abbreviation used for Christi here? The only thing I can read there is some unidentifiable symbol followed by "rpi" and I do not understand that.
I think it is the Christ monogram ΧΡ, followed by the genetive ending -i. Those are not the Latin letters X and P, but rather the Greek letters Chi and Rho, which are the first letters in the word ΧΡΙΣΤΟΣ (Christos). This is one of the oldest and most famous Christograms, but usually the letters are on top of each other.
In this case they appear to have been written like Latin letters though.
The "unidentifiable symbol" is just a bit of the last a from famula colliding with the x.