What it means
には及ばない expresses that an action is unnecessary or excessive under the circumstances, meaning “there is no need to” or “it is not necessary to go so far as to.” It is a formal, restrained expression often used to reassure someone or to decline an action without sounding abrupt. The polite counterpart is には及びません.
Usage note
には及ばない can also be part of the literal meaning “does not reach” or “falls short of,” especially when it follows a noun or refers to a level or standard. The “there is no need to” meaning normally follows a verb in the dictionary form, as in 説明するには及ばない.
How to use it
その件については、今ここで詳しく説明するには及びません。
Regarding that matter, there is no need to explain it in detail here now.
その件については、今ここで詳しく説明するには及ばない。
Regarding that matter, there is no need to explain it in detail here now.