Matches spans near the beginning of a field. The span first query maps to Lucene SpanFirstQuery. Here is an example:

GET /_search
{
    "query": {
        "span_first" : {
            "match" : {
                "span_term" : { "user" : "kimchy" }
            },
            "end" : 3
        }
    }
}

The match clause can be any other span type query. The end controls the maximum end position permitted in a match.