The Tiferes Shlomo explains this pasuk with the words of the Gemara (Pesachim 64B): “Ain maavirim al hamitzvos.” (Do not pass by mitzvos.) He explains that a tactic used by the yeitzer hara is to try to convince a person he is unworthy of serving Hashem. It tells him: “Why are you? You have committed so many sins. How do you have the chutzpah to daven to Hashem.”
The truth is, however, that Hashem hears every prayer, and He is merciful and compassionate to all people. The words “ain ma’avirim al hamitzvos” mean that no one should think about the aveiros he has done (the word “ma’avirim” can be understood as a reference to aveiros), at the time that he is doing mitzvos. Regarding this, the pasuk says (Tehillim 34:14): “Sur mei’rah v’asei tov.” (Stay away from bad and do good.) This means that at a time when someone is doing something good, he should not think about the bad things that he did in the past.
This is also the meaning of the words “and he came down from making the Chatas.” At the time when Aharon blessed Klal Yisroel, he did not think about their sins (chatas) of the past.
Furthermore, this is the meaning of the pasuk (Tehillim 69:14): “V’ani tefilasi lecha Hashem eis ratzon.” (And for me, may my prayer to You, Hashem, be in an acceptable time.) This means that one should always daven to Hashem with the assurance that the tefillos will be accepted and it will be an acceptable time for prayers, no matter when it is.
