פירוש על מעשר שני 5:11

ולא מן התלוש על המחובר וכו' – that is from that which is obligatory for that which is exempt, and from that which is exempt for that which is obligatory.

Introduction This mishnah continues to expound up Deuteronomy 26.

ולא מן החדש על הישן – as it is written (Deuteronomy 14:22): “[You shall set aside] every year [a tenth part of all the yield of your sowing] that is brought from the field,” and not from this year for its neighboring year.

“According to all Your commandments which You have commanded me,” thus, if he took out maaser sheni before the first tithe he cannot make the confession. The confessor states that he has properly performed all of the mitzvot involved with separating tithes. The first issue is that he has performed the tithes in their proper order. He didn’t take out maaser sheni before he took out first tithe (see Terumot 3:6).

ולא שכחתי מלברכך ומלהזכיר שמך עליו – since we recite a blessing to separate the heave-offering/sacred donation [to the Kohen], and similarly on the First and Second Tithes and the Poor Tithe, and for the redemption of the Second Tithe, and for Hallah, on all of them we recite a blessing.

“I have not transgressed any of Your commandments” I have not set apart [tithes] from one kind for a different kind, nor from plucked [produce] for [produce still] joined [to the soil], nor from new [produce] for old [produce], nor from old [produce] for new. He now confesses that he didn’t do anything else that is prohibited when it comes to tithing. We have learned all of these issues before (see Terumot 1:5, 2:4). Basically, one has to give terumot and maasrot from like produce, and one can’t separate one type of produce in order to exempt another.

“Neither have I forgotten” I have not forgotten to bless You, nor to make mention of You name over it. When one separates terumah and tithes, one must make a blessing, “Who has sanctified us with His commandments and commanded us to separate terumot and maasrot.” “I have not forgotten” is a reference to the fact that he didn’t forget to recite this blessing.