Tafsiran Kejadian 30:18: Rashbam, Radak, Chizkuni & Tur HaArokh

יששכר, a double reward, one for handing over the dudaim; the other, that I gave my handmaid to my husband to have children with.

ותאמר, seeing that she had stopped bearing children and had given her maidservant to Yaakov in her stead, she thought that she had been rewarded for this by G’d (for two reasons; 1) for helping her husband to father more children so that his indulging in sexual intercourse with a woman who could not provide him with children would not be accounted as mere physical gratification. 2) for having done her maidservant a great favour to become able to mother the children of such a righteous man as Yaakov. For both of these reasons she expressed the hope that G’d would reward her. When she subsequently indeed bore children for Yaakov again herself, she considered this as her reward from G’d and thanked Him for it. She made certain that her son’s name reflected her feeling of gratitude by naming him יששכר.

נתן אלוקים שכרי אשר נתתי שפחתי לאישי, “G-d gave me my reward for having given my maidservant to my husband.” She acknowledged G-d’s generosity, by having realised that if her sister had become a mother only vicariously by having given her servant maid to her husband, she had had good reason, as she had failed to personally provide him with children, and this was excusable; she, Leah having done so also was probably inexcusable; if nonetheless G-d had blessed her with having two more sons to raise, she considered this as a reward for her generosity in offering Yaakov her servant maid as a wife. In light of these considerations she named this son יששכר, “he who will be the symbol of a reward.” The name is written with two letters ש to draw our attention to what she meant.