The death of these priests was not, however, unmerited, for in spite of their piety they had committed many a sin. Even at Sinai they had not conducted themselves properly, for instead of following the example of Moses, who had turned his face away from the Divine vision in the burning bush, they basked in the Divine vision of Mount Sinai. Their fate had even been decreed, but God did not want to darken the joy of the Torah by their death, hence He waited for the dedication of the Tabernacle.
On this occasion God acted like the king who, discovering on the day of his daughter's wedding that the best-man was guilty of a deadly sin, said: "If I cause the best-man to be executed on the spot, I shall cast a shadow on my daughter's joy. I will rather have him executed on my day of gladness than on hers." God inflicted the penalty upon Nadab and Abihu "in the day of gladness of His heart," and not on the day on which the Torah espoused Israel.