Musar su Isaia 42:21

The fact that her age is alluded to first in the name צחק is to indicate that she was not merely an appendix to her husband. We have a similar situation when the Torah reports that Moses first relayed G–d's words to the women at Mount Sinai. We read in Exodus 19,3: "Thus you shall say to the house of Jacob (women), and tell the children of Israel." The reason that the women were addressed first, and of course expressed their willingness to accept Torah first, was to prevent anyone thinking they had done so only to please their husbands rather than to please G–d. Sarah similarly proselytized independently from her husband. Since Genesis 12,5 is the beginning of the gift of Torah, it is appropriate to mention the part a woman played first. The word צדיק spelled as words, צדיק-דלת-יוד-קוף, contains an allusion to the giving of the Torah as we know from ה' חפץ למען צדקו יגדיל תורה ויאדיר.