What is a cowardice in Buddhism?

Cowardice is harmful for it delights the enemies of Buddhism and obstructs the advance of kosen-rufu. The fainthearted cannot savor the true benefit of faith; their ability to tap the power of the Buddha and the power of the Law [of the Gohonzon] in their lives is enfeebled.

For Today and Tomorrow
Daily Encouragement by Daisaku Ikeda 5/6

Cowardice is harmful

Cowardice is harmful for it delights the enemies of Buddhism and obstructs the advance of kosen-rufu. The fainthearted cannot savor the true benefit of faith; their ability to tap the power of the Buddha and the power of the Law [of the Gohonzon] in their lives is enfeebled. 5/6

Courage and compassion are inseparable

Without courage we cannot be compassionate. Courage and compassion are inseparable, like the two sides of a coin. Faith is the wellspring of courage. The Daishonin says, "Nichiren's disciples cannot accomplish anything if they are cowardly," (The Major Writings of Nichiren Daishonin, vol. 1, p. 128). A cowardly person cannot realize victory in life. Unless we have the courage to really dedicate our lives to kosen-rufu, we cannot construct true happiness for ourselves and others. 23/2

Cowardice is harmful

Cowardice is harmful for it delights the enemies of Buddhism and obstructs the advance of kosen-rufu. The fainthearted cannot savor the true benefit of faith; their ability to tap the power of the Buddha and the power of the Law [of the Gohonzon] in their lives is enfeebled. 5/6