What is Temimus?
Rabenu Yona (in Sefer Sefas Tamim, Perek 17) speaks about temimus at length. He writes:
The mailoh of temimus is very great and precious. If one walks with temimus, Hashem desires him and his praises, as is stated (Tehillim 101:6): “One who walks in the ways of a tamim, he shall sing to Me.” And Moshe Rabenu commanded us about the concept of temimus, as stated: “Tamim tihiye im Hashem Elokecha.”
Temimus is so great that anyone who walks with simplicity of the heart in all of his ways merits to sit in the chamber of Hashem, as is stated (Tehillim 9:4): “Who shall dwell in His tent? He who walks as a tamim.” And Dovid praises those who walk with temimus, as is stated (ibid 109:1): “Praiseworthy are those who are temimei derech.”
Rabenu Yona continues: What is temimus? One should speak without any trickery and do business honestly. His mouth and heart should be as one. Anyone who says one thing with his mouth and thinks something else in his heart is not called a “tam”; rather, he is a swindler and crook....But if one walks with temimus, Hashem assists him in his work...
Temimus is so valuable to Hashem that he desires anyone who walks with temimus...Furthermore, as a result of temimus, He prepares a straight path for a person, as is stated (Mishlei 11:5): “The righteousness of a tamim straightens his path.” If one acts with temimus with Hashem and with other people, He protects him from sin and he can live serenely and securely, as is stated (Tehillim 18:24): “I was tamim with Him and He protected me from sin.”
