bhaktyāveśya mano yasmin
vācā yan-nāma kīrtayan
tyajan kalevaraṁ yogī
mucyate kāma-karmabhiḥ
May he remain here (pratiksatam) until I, after some time, after drinking the sweetness of his beauty with my eyes, after I praise him and reveal what is in my mind, give up my body. May he with four arms, who should at all times be the object of my meditation, since he is my object of worship, with his pleasing form and smile, remain directly in front of my eyes at the time of my passing from the body.
Bhisma addressed him as a form with four arms because that was the form of Krsna mentioned in the mantra he used during meditation.