What made Yitzchak bring Yaakov close to feel him?
Some commentaries explain that this was because he was constantly out in the forest, an environment that was generally unclean. The Oznayim la'Torah however, attributes it to the fact that Esav, who did not believe in HaSh-m and his Torah, thought that Ma'aser was an act of kindness to the poor. Consequently, he asked his father why it should not apply equally to straw and salt, which a poor man also needs. Yitzchak assumed that since Esav was performing the Mitzvah she'Lo Lishmah, he would eventually come to perform it Lishmah. What he did not realize was that Esav was only asking these questions to trick him - because he had his eye on the Berachos, but in reality, he was not averse to performing every atrocity under the sun.
Why does it say, "va'Yomer Yitzchak El Yaakov"? The previous verse said "El Beno" (27:20)!
Malbim: Initially Yitzchak was unsure of the voice, and wanted to test him, so it says Beno. He then hearkened to the voice, and the words of Yir'as Shamayim and Emunah, and recognized that it is Yaakov. He then tested by feeling him, which clarifies more than the voice does.
QUESTIONS ON RASHI
Rashi writes: "Approach, please, and I will feel you - ... [Yitzchak said,] Esav does not commonly use the Name of HaSh-m!" Why not? We know that Yitzchak assumed Esav to be worthy!
Ramban: Yitzchak assumed that because Esav was a hunter, he refrained from using HaSh-m's Name for fear that he might mention it in impure places or without proper intent.
Gur Aryeh: Yitzchak judged Esav favorably, assuming that he served HaSh-m out of Yir'ah, and did not mention HaSh-m's Name, due to fear of Him. He assumed that Yaakov served HaSh-m out of love, and therefore he constantly mentioned HaSh-m's Name. Because Yitzchak himself had he trait of Yir'ah, he was drawn to love Esav.
Rashi writes: "Esav does not commonly use the Name of HaSh-m!" Why does Rashi explain that this led to Yitzchak's suspicion, more so than Yaakov's voice?
Gur Aryeh: Yitzchak did not immediately ask Yaakov to approach him when he first identified himself as Esav; their voices must have been similar. Refer to 27:21:151.3:1.
Rashi writes: "Esav does not commonly use the Name of HaSh-m!" Why was Yitzchak suspicious only now, and not immediately upon hearing Yaakov's voice (rather than Esav's) in verses 27: 18-19?