1 Samuel 14:35 - Ellicott's Commentary On The Whole Bible

The same was the first altar that he built... — More accurately, as in margin, the same he began to build as an altar. The great Jewish commentators are divided as to the precise meaning of the old Hebrew language of this verse. Abarbanel interprets the words, “that King Saul began to build, but did not finish.” The Midrash prefers to understand the statement as telling how “Saul began among the kings of Israel the building of altars.” The more obvious meaning, if we translate as in our English Version, seems to be that this was the first public acknowledgment King Saul made to God for the mercies and goodness vouchsafed to him.