In Greek, hold to one means cleave to the one as against the other. This indicates that to serve the Lord requires us to love Him, giving our heart to Him, and cleave to Him, giving our entire being to Him. Thus we are released from being occupied and usurped by mammon, that we may serve the Lord wholly and fully. The Lord emphasizes here that to serve Him we must overcome the enticing, deceitful mammon of unrighteousness.