The Midrash (Kohelet Rabba 10) finds it significant that Noach did not enter the ark to escape from the flood until God instructed him to do so (7:1), and did not exit the ark after the flood until God instructed him to do so (8:16): “He entered the ark with permission, and left with permission.”
Commenting on the significance of Noach’s leaving the ark only with God’s permission, Rav Yehuda Leib Ginsburg writes in his Yalkut Yehuda that Noach could not leave the ark before receiving God’s authorization because his sojourn in the ark served as a means of atonement. Elsewhere (Bereishit Rabba 31), the Midrash comments that the ark “purified” Noach, comparing the ark to the process of purification that a metzora must undergo before he can return to his city. This comparison clearly indicates that Noach, while having resisted the sinful influences of his contemporaries, was nevertheless guilty of certain misdeeds for which he required atonement, just as a metzora’s condition – as understood by Chazal – resulted from certain transgressions. The grueling experience of living in the ark with the world’s animals, the Midrash teaches, was Noach’s means of attaining atonement so he could be worthy of being saved from the flood. Accordingly, Rav Ginsburg writes, Noach had to endure the cramped, harsh conditions of the ark even after the floodwaters subsided until God determined that his process of atonement had been completed. For this reason, he waited until God’s explicit command to exit the ark before leaving, as only God could determine when he had satisfactorily completed his atonement process.
Extending this notion further, we might suggest that Noach waited to enter the ark for the same reason. Although he may have been eager to achieve atonement, he was not entitled to begin this process before the time God determined this was to occur. Just as Noach could not complete his atonement process before receiving God’s instruction, he likewise could not begin his atonement process before receiving God’s instruction.
If so, then the Midrash emphasizes that we are not entitled to determine on our own the proper way to attain closeness to the Almighty. No matter how sincere we might be in our desire to draw close to God and to serve Him, we must “wait” to receive His command; we need to follow His guidance and instructions for how to serve Him, as conveyed to us through our Torah tradition. Just as Noach could not decide on his own when and how to experience the “purification” provided by the ark, similarly, we must not try to decide on our own how to achieve purification, sanctity, and closeness with our Creator, and must instead faithfully abide by His commands and the dictates of the halakhic system.