Provided is a method for a first device to perform wireless communication. The method may include the steps of: receiving a configured grant from a base station; transmitting a first transport block through a first sidelink resource related to a first hybrid automatic repeat request (HARQ) process ID and allocated by the configured grant; failing to transmit the first transport block; and transmitting a second transport block through a second sidelink resource related to a second HARQ process ID and allocated by the configured grant, on the basis of the second HARQ process ID related to the second sidelink resource being the same as the first HARQ process ID.