A great 3B flare, whose X-ray class was X13, occurred over a delta-sunspot at 00: 01 UT on April 25, 1984. Before the flare, a strong magnetic shear was found to be formed along the neutral line in the delta-sunspot with shear motions of umbrae. The shear motions of the umbrae were caused by the successive emergence of a magnetic flux rope. Before the flare, several groups of sheared Hα threads and filaments were found to merge into an elongated filament along the neutral line through the delta-sunspot. In the merging process the helical twists were formed in the filament by the reconnection as in the Pneuman's (1983) model. At the post-maximum phase of the flare, the helically twisted filament spouted out with an untwisting rotation. Examining the morphological and dynamical features of the filament eruption, we concluded that it has some typical features of the flare spray and that it seems to be accelerated by the sweeping-magnetictwist mechanism proposed by Shibata and Uchida (1986).