QUESTION: Why in the first
pasuk does Hoshea say
"ad Hashem," while in the following
pasuk he says
"el Hashem" - "to Hashem"?
ANSWER: A person's sin can be either bein adam laMakom - between man and Hashem - or bein adam lachaveiro - between man and his fellow. In both cases the person must strive for forgiveness. However, for sins of the first nature one must repent, pray and supplicate Hashem. For the latter, forgiveness is accomplished by appeasing the person wronged.
The Mishnah (Yoma 85b) says, "Sins between man and G-d, Yom Kippur atones; but sins between man and his fellow, Yom Kippur does not atone until he appeases his fellow." Carefully analyzing the wording of the Mishnah, commentaries suggest that the Mishnah is teaching that if one committed both categories of sins, Yom Kippur will not atone the sins between man and Hashem, unless the sinner first appeases his fellow for the iniquity committed against him. (See Rif to Ayin Yaakov, Birkei Yosef 606 and Mateh Efraim).
In fact, every time a person commits a sin against his fellow he is simultaneously committing a sin against Hashem, and Hashem does not forgive his part until man forgives his (see Pri Chadash to Orach Chaim 606).
The word "ad" sometimes means "before." As we say in the daily morning prayers, "Atah hu ad shelo nivra ha'olam" - "You were [the same] before the world was created." Consequently, the prophet's message can be explained as follows:
"Shuvah Yisrael" - "O Israel do Teshuvah" - repent among yourselves, ad - before - i.e. prior to repenting for what you did wrong to Hashem your G-d.
"Kechu imachem devarim" - "take words among you" - the way to deal with sins committed among yourselves, is by approaching your fellow with soothing words and begging his forgiveness. [Afterward] "veshuvu el Hashem" - "return - i.e. repent - to Hashem" for the sins committed against Him.