GEN775 We should offer others our blessings.  … When the Torah states that God will bless “those who bless you,” it refers not only to someone who blesses Abraham, but also to someone who blesses a descendant of Abraham. Chulin 49a.  Rabbi Yechezkail Levenstein cited this verse in a letter he wrote to show that blessing one’s friend is a very worthwhile action.  When you bless another person, you merely offer a few words, in return for which the Almighty give you His bountiful blessings.  (Ohr Yechezkail, p.4).  Remember—when you greet a fellow Jew with a cheery “Good morning” or “Good night,” you are blessing him, and you will be blessed.  Don’t merely mumble the words.  Be sincere and keep in mind that in essence you are saying, “I pray that you should have a good morning.” (Eved Hamelech, Brashis, p. 51a). It is fitting to give a blessing for success to one who embarks on a business venture or undertakes a new job. If, however, the work being done is prohibited by the Torah, it is forbidden to give a blessing.  Mishnah Berurah 346:7.  PLYN 44-55