John Calvin on Matthew 16:25

25. For he that would save his life shall lose it. It is a most appropriate consolation, that they who willingly suffer death for the sake of Christ “Ceux qui meurent alaigrement pour Christ;” — “those who die cheerfully for Christ.” do actually obtain life; for Mark expressly states this as the motive to believers in dying — for my sake, and for the sake of the Gospel — and in the words of Matthew the same thing must be understood. It frequently happens that irreligious men are prompted by ambition or despair to despise life; and to such persons it will be no advantage that they are courageous in meeting death. The threatening, which is contrasted with the promise, has also a powerful tendency to shake off carnal sloth, when he reminds men who are desirous of the present life, that the only advantage which they reap is, to lose life. There is a contrast intended here between temporal and eternal death, as we have explained under Matthew 10:39, where the reader will find the rest of this subject. Harmony, vol. 1 p. 472.