Rashi on Genesis 48:14/רש"י על בראשית מ״ח:י״ד

1שכל את ידיו PLACING HIS HANDS DESIGNEDLY — Understand this as the Targum renders it: אחכמינון he put wisdom into them (viz., into his hands), meaning designedly and wisely he moved his hands for this purpose, intelligently and with full knowledge, for he knew that Manasseh was the first-born and yet he did not place his right hand upon him.