Ibn Ezra on Numbers 28:7

הסך נסך שכר. נו"ן השורש מובלע בסמ"ך ומן הפירוש נסמוך על דברי הקדמונים ז"ל: SHALT THOU POUR OUT A DRINK-OFFERING OF STRONG DRINK. The stem nun¹⁰Of the root nun, samekh, caf, the root of hassekh (shalt thou pour out). is swallowed by the samekh.¹¹In the word hassekh (shalt thou pour out). Hence the dagesh in the samekh. We will rely on the words of our sages of blessed memory as to its meaning.¹²We will rely on the sages concerning what Scripture means by the term nesekh (strong drink). According to the sages it refers to undiluted wine. In ancient times wine for drinking was mixed with water.