מדרש על ויקרא 27:10

2) I might think that dedications to Temple maintenance (bedek habayith) are (also) susceptible of substitution (viz. Vayikra 27:10) it is, therefore, written "offering" — to exclude dedications to Temple maintenance, which are not offerings.

3) I would then exclude dedications to Temple maintenance, which are not offerings, but I would not exclude communal dedications (of offerings); it is, therefore, written (Vayikra 27:10) "He shall not exchange it." I would then exclude communal offerings, but I would not exclude offerings in partnership; it is, therefore, written (again) "and he shall not substitute for it" — An individual can make a substitution, but not the community or partners.

5) (Vayikra 27:10) "and he shall not substitute for it." The consecrated animal is susceptible of substitution, but not its substitute. R. Yehudah said: And the offspring (consecrated animals) are not susceptible of substitution.