Wholehearted mitzvos can bring redemption

ואיתא במד' אילו הי' יודע בועז שהקב"ה כותב עליו ויצבט לה קלי עגלות פטומים הי' נותן לה וכן בראובן על כתפו הי' מוליכו לומר כשאדם עושה מצוה יעשנה בלבב שלם כו' ע"ש.

And it is brought in the Midrash: Had Boaz known that the Holy One, Blessed is He, was recording about him "and he handed her parched grain," he would have given her fattened calves; and likewise, had Reuven known, he would have carried Yosef back on his shoulder [to his father] — to teach that when a person performs a mitzvah, he should do it with a whole heart, see there.

The Midrash observes that these tzaddikim did good deeds without realizing how eternally significant they were. Boaz gave Rus a modest portion of roasted grain; Reuven saved Yosef from the pit. Had they grasped that the Torah would immortalize their acts, they would have done far more. The lesson: do every mitzvah wholeheartedly.

ונראה שאלה האנשים אשר עשו מצוה בשלימות שנתקבל לפניו ית"ש אם היו מתחזקים ביותר הי' מיד גאולה שלימה.

And it appears that these men, who performed a mitzvah in completeness such that it was accepted before Him, Blessed is His Name — had they strengthened themselves even more, there would immediately have been a complete redemption.

The Sefas Emes pushes the Midrash further: their deeds were already so pleasing to Hashem that just a bit more wholehearted effort could have triggered the final geulah on the spot.

וראובן היו מספיקין בידו להשיבו אל אביו ולא היה שוב גלות.

And as for Reuven — they would have granted him the means to restore [Yosef] to his father, and there would no longer have been galus.

Had Reuven completed his intended rescue and brought Yosef home, the entire descent into Mitzrayim and the galus that followed could have been averted.

וכמו כן בבועז אם הי' מתחזק בחסד זה ביותר הי' משיח בא מיד.

And similarly with Boaz — had he strengthened himself in this chesed even more, Mashiach would have come immediately.

Since the line of Mashiach issued from Boaz's act, a more complete performance of that very chesed could have brought Mashiach at once.

כי בכל מצוה נכלל כל התורה ותחה"מ כמ"ש לעיל:

For within every single mitzvah the entire Torah and techiyas hameisim (the resurrection of the dead) are included, as was written above.

As explained in the previous piece, each mitzvah, done fully and lishmah, contains the whole reviving power of the Torah — which is why a single wholehearted act has the potential to bring complete redemption.

Summary: Boaz and Reuven did their mitzvos without realizing their cosmic weight; had they acted with even greater wholeness of heart, the geulah could have come at once. Because every mitzvah contains the entire Torah and the power of techiyas hameisim, even one complete, wholehearted deed holds the potential to bring the final redemption.