Tosefta к Маасро́т 5:12

One who leaves behind [tithed] produce at the place of a Samaritan, behold, they are presumed to [retain their status] for tithes and for Shevi'it, and if they were untithed, he takes Terumah and tithes for them from another place (i.e., from other untithed produce, see Maasr. 5:6), or he designates the Terumah portion of the tithes from them. If they were from second tithe, he exchanges them for money, and he exchanges the money for the second tithe. If [the Samaritan] says to him, "I took it and I exchanged it for you for old [produce] in its place," or "[I exchanged it] for tithed [produce]," behold he should not be concerned about them (i.e., the produce) with respect to tithes or with respect to Shevi'it.